To pick up your hamster:

Cup the hamster, preferably with both hands. They might try to jump off and so do be careful of that. Hold them over a table or their tank so that if they do fall, they won't run away or get hurt.

I have found that campbells are generally nippier and some will even "fly" at your hand to take a bite out of it. You can try using a toilet roll to pick up your hamster. Some owners also use gloves to handle their campbells but I don't think this really helps your hamster to get used to you. If you wish to do this, remember to wear thick gloves as your hamster will easily bite through thin cotton ones.

Useful links

A page on Handling Hamsters at the Association of Pet Care Counsellors