Stick to the shadows, spotting a disciplined sniper shooting out of a shadow is no easy feat. If they have the Camouflage badge you won't have any clues upon being nailed by them either.
Always go prone, your weapon is far more stable.
Discipline...go for the high probability shots. It is better to let four moving targets go and wait for that one guy who is going to oblige you by stopping. The other benefit is that you stretch out your ammo and you do not give away your position as readily. Once you have played this game enough you can tell the difference between the report from the different sniper rifles. Especially helpful when you are hunting enemy snipers. A quick check of your map will let you know if a friendly is nearby that picked up an enemy sniper rifle.
Movement is your enemy. A moving target is far more easy to spot than a stationary one.
Pick your spot carefully. If you watch players they tend to go in the straightest line from spawn to objective. I tend to go with locations that provide flanking shots, with nearby cover that I can fall back to. I avoid buildings as much as possible, my camouflage is pretty useless inside buildings and it is one of the first places I look for enemy snipers and surprisingly find them a lot. If you can find a bush in a shadow with a good flanking view that is optimal.
A sniper is a support weapon, if I can setup behind or flanking a friendly tank I can help keep enemy tank hunters from closing in on them. Equally viable is to cover an entrance or a ladder on an objective that would be a natural draw for the enemy to go for. Again taking objectives is not something that I advocate a sniper doing, you simply do not have the firepower for close quarters battles.
Weapon build, I go for damage with the optimal kill range normally being 200 meters. Again, high probability shots are the order of the day when you get to 300 meters your accuracy falls of a great deal. I only take one pouch of ammo and take a Luger as a backup.
Kar98 Sniper Rifle
Ammo Anschusspatrone s.S.
Scope ZS Zielacht (fine cross hairs)
Trigger Fine Hair Trigger
Internal Heavy Bolt
Barrel Chrome Moly 4150
Ammo Wulff Engel
Sight Match Sights
Trigger Match Trigger
Internal Light Pistol Spring
Barrel Chrome Lined Barrel
Badges Nimble and Camouflage
Final thoughts...the sniper is a long range hitter as soon as you move into a building you are going to be at a disadvantage. Even with your Luger (or other pistol) you are no match for a competent player armed with a smg when you get rushed. A lot of snipers will use a motorcycle or bicycle to get into position, normally parking pretty close to where they are setting up at. It is one of the first signs I look for when hunting other snipers. I generally use a bicycle but will park it a fair distance from where I am going to be setting up at.