PPL-T,
Welcome to the club! It's a great road you've started down and a whole world of new experiences await!
Straight taxying is a bit like that elusive golf shot that actually goes where you wanted it to go. It happens, but not all that often!
Actually, taxying, like anything, comes with practice and you WILL get the hang of it. Every airplane is different, just like every car is different, and they all take a little bit of getting used to. It'll happen. Just remember that, more than keeping it on the yellow line (when there is one), the important thing to remember is not to hit anything. Everything after that is really just gravy.
Pitts2112