I'd say, be confident, be casual. Don't word things like an English major. Just say, "Mind if I put my arm on your shoulder?" Or if you feel like not touching them, just give a thumbs-up, or put your hands on your side, or cross your arms...
Limp noodle arms are the bane of picture-taking. xD
facebook page // nh/mass cosplay events
Next event: ???
COSPLAYS IN PROGRESS
Gig (Soul Nomad) - Constructing
Vaati (LoZ Minish Cap) - Planning
Soren (Fire Emblem: Radiant Dawn) - On hold