The best thing you can do is get or make a checkering cradle before you even start. GOOD EYES, good side light, sharp tools and frequent rests. When the cutter gets dull you will start pushing harder and that is when mistakes happen. Don't stretch, move your body. If you get out of your giude line, stop right there. Start your line again past where the mishap happened and then come back to the errant line from the other direction. The harder the wood, the finer the LPI you can use. If you hit a soft spot, AND YOU ARE NOT GOING TO STAIN THE WOOD, mix some wood glue with water and brush it on the spot. After it dries it will be noticably harder.
Bill
Bill