You will get this achievement via normal play but it will take a bit of time to get. You can decrease the amount of time it will take to get the 100 tracks by specifically targeting the enemy’s tracks but this could get you killed if not done correctly and you’d be better off killing the enemy not just tracking them.
It’s easiest to track a tank by aiming at the front or rear drive wheel (first or last wheel in the series on either track). If you do this from the side you will usually track the tank and cause damage. If shooting the tank from the front you will usually just track without causing damage. Here is an example of how to effectively track and damage a tank plus enable your team to cause further damage while it is disabled.
The best times to track the enemy are:
1) If you can track and
damage the enemy by hitting their drivewheel from the side.
2) If they can’t shoot back as they're driving a TD (have no turret) and you can stay out of their arc of fire.
3) If they can’t shoot back because their gun is behind hard cover.
4) If they can’t shoot back because you're above or below thier guns arc of fire.
5) If you have teammates that can concentrate fire onto a tank that can’t retreat once you’ve tracked it.
6) If you are bottom tier and can’t penetrate/damage top tier tanks armour then shoot their track so your teammates can kill them more easily (using high explosive (HE) ammo is very effective for this). You will get ‘assist damage’ for doing this which is a really good way of earning more XP & silver plus being useful for your team when you’re bottom tier in a match.
Using good tracking play will help you get better results and make some of the other achievement grinds a bit shorter due to more XP earned when bottom tier.