Sex help!

My boyfriend & I will be having (oral) sex some time soon in our relationship for the first time. We've both consented to all activities that will happen before & after the oral sex. I've never went down on a guy before, but I would like to on him, & he's given me permission to. he's also said that he'll help me out since I'm not skilled in going down on people. My question is, would it be better if I spit or swallow his cum/sperm? I'd really appreciate all advice because I was really nervous to ask. I'm 21, & he's 20.