Long, straight drives only happen when you catch the ball on the sweet spot and swing slightly in-to-out as you approach impact. Problem is, most rec players swing slightly (or extremely) out-to-in (as in, left of the target). A visual aid can help. Set up a yoga block (or any soft brick-shaped object) about one inch outside the ball after you've teed up. Use the block as a guide to steer your club on the correct downswing path.