It seems the same questions pop up again and again so hopefully this will help a little. I'm obviously not going to put on a public forum everything I use to try to pick winners but here are some basics that may be a good start for someone with limited tennis betting knowledge. I'll keep adding to it as I think of more things and anyone who wants to offer any insight or differing opinions, please feel free to do so. 
1. The lines in tournaments become sharper as the week progresses. Seems obvious enough as linesmen will be able to gauge a player's form and motivation as the week goes on and there are fewer players to focus on, but I repeatedly see people upping their stakes in 'big' matches. If you think about it logically, as the field shrinks, the weaker players are usually gone which narrows the gap between two opponents. Why suddenly up your stakes on a match when there's actually a better possibility of either playing winning?
2. Line movement and beating the closing number doesn't carry the same importance in tennis as it does in other sports. Lines are easily manipulated by books to encourage steam and name chasers and because the markets for smaller tournaments are considerably smaller than in a Slam, it doesn't take a lot of money to move a line. Cap your match, determine which player you think will win and assign a % chance of winning and THEN check out the lines. If the price you can get implies a higher chance of winning than your %, place the bet. It's a very simple theory and it works yet people seem to get stuck on this time and time again.
3. There are fixes in tennis and there probably always will be. There are also reverse fixes where an individual or group is toying with the lines in order to drive up the price on a dog as well as the market manipulation by the books I mentioned earlier. This is just a fact of tennis betting and the best advice I can give you is almost a repeat of #2 - When you see lines start to plummet, DO NOT JUMP ON BOARD. If you've placed your bet before the heavy movement started, you may want to cash out if it's moved in your favour to guarantee yourself a profit no matter how small and save yourself the grief. If the line has moved against you quickly, I'd suggest just sticking with your original bet and crossing your fingers that your player pulls it out. Many times people have laid heavy chalk to jump off a bet that looks like a sure loss only to see their original player win, costing them a lot of money in the end.
4. Live betting is a great tool for tennis but it's also a dangerous one. Tennis isn't like other sports where you can gradually see a momentum shift to one team. There are times when a player tanks a set to conserve energy for the next one. There are other times when a player looks like they have the match won but goes on to lose because they've used all of their energy to get that far and they start to commit unforced errors or lose the ability to serve. Be very careful with live betting, especially if you're trying to chase your losses on your initial bet. And don't ever live bet if you're just looking at a scoreboard. Stats and scorelines can be deceiving - they don't factor in how a player is moving, if they look fatigued, if that medical timeout was legit or was a stalling tactic or if a player is starting to become unhinged mentally between points. You can't underestimate the value of watching the match live.
5. You need to invest the time to learn about individual players and try to determine their motivation for each tournament and even each match. Go to the ATP website or even Wikipedia and learn about the point system that's used to determine a player's ranking. Learn what a protected ranking is and why it can be an important factor in a match. Google the hell out of a player before you put money on them - you'll find the most amazing things straight from a player's mouth on their own website, on Twitter or Facebook, and in interviews that you need to Google Translate from a foreign language (players seem to be more forthright when talking to their home media). Are players double partners? Are they from the same country? Do they need to protect points or is the tournament somewhat meaningless other than possibly collecting a paycheck? These are just a few of 100+ questions you could literally focus on if you want to have your best shot at picking a winner. But even if you don't find all the answers you need, you should still have a few more tools to help you to determine how much, if any, you should consider risking on a player in any given match.
1. The lines in tournaments become sharper as the week progresses. Seems obvious enough as linesmen will be able to gauge a player's form and motivation as the week goes on and there are fewer players to focus on, but I repeatedly see people upping their stakes in 'big' matches. If you think about it logically, as the field shrinks, the weaker players are usually gone which narrows the gap between two opponents. Why suddenly up your stakes on a match when there's actually a better possibility of either playing winning?
2. Line movement and beating the closing number doesn't carry the same importance in tennis as it does in other sports. Lines are easily manipulated by books to encourage steam and name chasers and because the markets for smaller tournaments are considerably smaller than in a Slam, it doesn't take a lot of money to move a line. Cap your match, determine which player you think will win and assign a % chance of winning and THEN check out the lines. If the price you can get implies a higher chance of winning than your %, place the bet. It's a very simple theory and it works yet people seem to get stuck on this time and time again.
3. There are fixes in tennis and there probably always will be. There are also reverse fixes where an individual or group is toying with the lines in order to drive up the price on a dog as well as the market manipulation by the books I mentioned earlier. This is just a fact of tennis betting and the best advice I can give you is almost a repeat of #2 - When you see lines start to plummet, DO NOT JUMP ON BOARD. If you've placed your bet before the heavy movement started, you may want to cash out if it's moved in your favour to guarantee yourself a profit no matter how small and save yourself the grief. If the line has moved against you quickly, I'd suggest just sticking with your original bet and crossing your fingers that your player pulls it out. Many times people have laid heavy chalk to jump off a bet that looks like a sure loss only to see their original player win, costing them a lot of money in the end.
4. Live betting is a great tool for tennis but it's also a dangerous one. Tennis isn't like other sports where you can gradually see a momentum shift to one team. There are times when a player tanks a set to conserve energy for the next one. There are other times when a player looks like they have the match won but goes on to lose because they've used all of their energy to get that far and they start to commit unforced errors or lose the ability to serve. Be very careful with live betting, especially if you're trying to chase your losses on your initial bet. And don't ever live bet if you're just looking at a scoreboard. Stats and scorelines can be deceiving - they don't factor in how a player is moving, if they look fatigued, if that medical timeout was legit or was a stalling tactic or if a player is starting to become unhinged mentally between points. You can't underestimate the value of watching the match live.
5. You need to invest the time to learn about individual players and try to determine their motivation for each tournament and even each match. Go to the ATP website or even Wikipedia and learn about the point system that's used to determine a player's ranking. Learn what a protected ranking is and why it can be an important factor in a match. Google the hell out of a player before you put money on them - you'll find the most amazing things straight from a player's mouth on their own website, on Twitter or Facebook, and in interviews that you need to Google Translate from a foreign language (players seem to be more forthright when talking to their home media). Are players double partners? Are they from the same country? Do they need to protect points or is the tournament somewhat meaningless other than possibly collecting a paycheck? These are just a few of 100+ questions you could literally focus on if you want to have your best shot at picking a winner. But even if you don't find all the answers you need, you should still have a few more tools to help you to determine how much, if any, you should consider risking on a player in any given match.
