Your main trade is really just E on the champion Q and start autoing them. I like to push lane with Tristana for a few reasons. First, you can't reliably freeze lane with Tristana because of her E passive (I know that pros and some high elo trists don't put points into E if they want to freeze). Second, since you have an easy escape (W) you can push lane to draw jungle pressure and are pretty safe if he comes, which wastes time for the enemy team and lets your other lanes relax a little. Third, she's good at harassing people under their towers, since she has longer range than most ADCs, and her E hits champions even if you cast it on the tower.

Try to gank her early, and do it often, rangers arent good against her unless she is stupid, and melee's need to be able to tank/blink to get to her as either way she will rocket jump away over terrain or ulti you into tower/her-team. If however you get flash and have a reliable stun/team, she's gone. If she has somehow farmed up super items you have to ambush and focus her whenever possible.
For tips to counter, i can only think of one massive hero. TEEMO!!! blinding dart makes her useless and the DoT is nice, plant shrooms where you think she will jump to escape/chase, and you got yourself a kill. Also anyone with burst damage is nice as 9/10 times Tristana will have the lowest hp in the game and will focus on dmg/att spd/crit, therefore no armor or magic resistance