2009 Update: My own students will quickly make Richmond their home location since they won't rez at the public Orientation Islands. Still...if you hit a Welcome Area, this advice will be useful.
Be careful when you arrive at a "Welcome Area" that will be your home base until you reset it to Richmond Island! All sorts of shady characters, and a few helpful ones (thankfully) hang out at these places.
Sometimes I go to these spots and mentor new arrivals. If you see "Second Life Mentor" floating above someone's head...ask them for help. But often random encounters are with helpul veterans.
Looks in SL can be deceiving. A dragon or devil avatar may be really helpful, and a mild-mannered "noob" avatar could be a griefer.
There is a roleplaying game based on vampires in SL. It's called Bloodlines and it can be annoying; many vampires run about and get points by asking if they can bite other avatars. I always tell them "no, I need my blood." They are not creeps per se, but they can be pests, not playing the game well but simply racking up points for the number of bites they collect.
Ask me for a garlic necklace if this gets at all annoying. It is an actual object to deter Bloodline players. The Bloodlines designer made the necklace, and it makes one invulverable to bite-requests. It even removes you from the Bloodlines vampiric database...wish I were joking.
My best advice in case of a close encounter with a creep: walk or fly away and find Richmond Island. Do not accept random friend requests or teleport requests. For those who come through Orientation Island, however, you will get them and they are almost always innocent.