The best way is to go very lightly. You have to go lighter on the lower than the upper lashes because they're usually not as thick.
Also, just practice, practice, practice in front of the mirror on a day when you have nothing better to do. You might be blinking some or your lower lid muscles quivering since it's not usually natural to be putting something that close to your eye. If you practice enough, you'll be able to put it on without having your muscles quiver. When I was young, my aunt told me she used to spend hours practicing putting on her mascara until she could do it right every time. When I wore makeup, I followed this advice until I could do it. Now, I hardly wear eye make-up, but whenever I do, it always looks as close to perfect as possible. It's like riding a bike, once you learn to balance, you have it down forever.
Edit to add: Joey posted at the same time as me, so I didn't see his tissue suggestion. This would work, but it's not necessary once you learn the amount of pressure you need and when to stop your hand from brushing it onto the lashes. Also, if you're wearing an under-eye concealer, you'll want to be careful since the tissue could possibly wipe some of it off since you likely put on the concealer before doing your mascara.
(On a side note, if you wear eye liner on your lower lid, you'll probably find that it'll start running after a few hours because of any sweat and oils on your face. The liquid concealer works great to prevent this, because you'll have concealer there to keep it from running down in any lines or wrinkles.)
