Tip #1 Always aim for the head. Headshots deal more damage. If you are not good in headshots then practice with bots not with online players because your skill will go down if you lose online.
Tip #2 Change position when you get killed
Tip #3 Be aware that the gravity hook leaves tracks. Shoot somewhere close again with the gravity hook so that the trails will not be seen by walking but only by looking up.
Tip #4 Upgrade the cloaking in your armor and get Diamond Polish, Elite, or Desert Camo
Tip #5 Get a good gun with untraceable bullets like Mag-Rail, Longshot(if there still will be one), Auto Rifle, or Ripper
Tip #6 Use the scope only when neccesary. Like when an ememy is hiding behind a wall and his foot is sticking out
Tip #7 Avoid unnecessary shooting. Enemies might hear your shot and thats the end of you.
Tip #8 Use Beserker Shields if you think you cant take down the enemy by your gun
Tip #9 When an enemy spots you, use the time that he/she is aiming at you and shoot him/her immediately in the head if you can.
Tip #10 When in close quarters combat run towards the enemy zigzagging and shooting him to disorient him/her. Once very close headshot him/her and it would be an instant kill if you have a high damage upgraded weapon.
Tip #11 Avoid staying in corners. You will be killed fast with splash damage rockets or killed with the ricocheting bullets of the devastator.
Tip #12 A gravity hook is a sniper's best friend. Get one.
Weapon: Mag-Rail, Gravity Hook