Don't be upset if you have to use the trim tabs on your transmitter. The items Twistr mentioned always seem to need attention, and even if there's a little imbalance or control surface offset, it's really not a big reflection of your building skills. We've all missed an alignment, at one time or another, and the plane still flew.

There is a larger issue, though, about flying straight and level. Mainly, you don't do much of it. Especially during the training period. The reason for that is, if you fly straight and level for any length of time, the plane gets too far away to see easily and control properly.

You will actually find that while flying, you are always either turning, or setting up your next turn. The time you spend flying straight will be minimal and may be a relief, but more than that it allows you time to think about setting up your approach, or your maneuver, or your simple turn. The turns are more important, in most cases.

Good to see you thinking ahead! Best wishes,
Dave Olson