It gets easier when they are a little older, but you didn't mention how old they are. It's not too bad when they are at least three weeks old, at 6-8 weeks even easier because their genitals are bigger. I like to use the 'punctuation' method. If their vent area looks like a ":", colon, then it's a buck. Also if you press on either side of the penis opening it will come up like a small volcano and the rim will be rounded, no penis coming out at this age. If it looks like an "!" exclamation mark, with the anus being the lower dot, then it's a doe. If you press on the sides of their vulva it will also protrude or stick out but one end of the slit will be kind of pointy and the other will be a bit rounded. It's very subtle. The best place, or at least the one with the most clear photos of rabbit sexing is here: http://www.rabbitnetwork.org/articles/sexing.shtml But the best thing is experience and learning what they look like at different ages and keeping a record of what you thought they were at certain ages and how they possibly change with age. Start at 2 weeks of age so you know what that looks like and you'll soon be able to tell on nearly any age rabbit.