Live Gourmet living butter lettuce is my favorite to use, because it DOESNT NEED TO BE CHECKED! (Yup you read that right)
You just need to make sure you cut the root off before shabbos, since it's technically still growing, and rinse off the dirt.
But when I buy other lettuce I use the OU method. Or the CRC method if I'm checking a lot, but I don't like to rely on it unless the batch has been really clean and bug-free.