A bullet comparator is the best way to go, and you will find that most good bullets measure within a couple of thousandths.
Without a comparator, just use two or three or four bullets to compare with each other to determine exactly where the lands are, and to determine the average OAL to the bullet tip. Ensure that they reasonably agree and that you didn't just happen to pick the shortest or longest bullet in the box.
As Steve says, as long as you know you aren't unintentionally hitting the lands, and you aren't exceeding reasonable pressures, just load, shoot and smile.
