What are the best tips/tricks for defending when playing PES on XBOX?
Try and either mark a runner, or keep yourself between the attacker and your goal. Don't feel the need to tackle them right away. If you slow them down, more of your team get behind the ball which makes things harder. That said, don't give them space to move or pass... Remember unlike attacking, you can't defend on your own. You need to place yourself with respect to where your team mates are: plug a gap in the defensive line, block a dangerous passing option and so on. Don't chase the player with the ball all over with the same player. This draws your players out of position and creates space for dangerous attacks.
Try not to run. This a concept that I used to learn to defend very well after I had already won several Master Leagues in the hardest difficulty. The idea is never to run and practice this. After a few games it will come easily and make you a stronger player.
The idea is that most of the time when you are defending you are running and if you stop doing that your entire defensive style changes. When you get used to not running you can start running again but you will have learned something new. Actually you will have a new timing strategy to tackle and also since you don't have to run so much you will have a much fitter and less tired team.
If you don't run it's much harder to make your team lose there positional form on pitch and your players wont be caught out of position. This will also help your positional sense and help you gouge there real value.
Finally when you don't run you can't slide tackle so much so you must use your normal tackle. If you use it a lot then your timing will improve and you will be able to get the ball easily. A well timed tackle can make a horrible defender impassable for all but the best players.
For the played game, the suggestions from other users are good; the first thing you would need to master is timing:
1. use slide tackle just when the ball is far from your opponent's feet
2. slow down your opponent first, let your other players return (on counter attack)
3. use double pressure (don't overuse it)
4. always use pressure
Anyway, the best trick to defence is to place your defence properly with strategy.
I really like to play with four defender and a midfield that stay very low to help the defence.
What i do is to change the behaviour of the two side defender to play like a central defender, i force them to play just in defence and to never cross the midfield.
This obviously give you less power\choices in attack but grant you a solid defence without fear of any counter-attack.