HowTo Hike Mt Katahdin

The key thing to know about Baxter SP is that it is heavily regulated. There is no camping outside of designated sites. If you don't have one reserved, I wouldn't get your hopes up, but it can't hurt to call and ask. You'r trip will probably be dictated by available sites, so again – best advice is to call. The website is:
http://www.baxterstateparkauthority.com/index.html

There are no loops from the W side of the mountain. Fron the east, it's possible. The approach is from Roaring Brook > Chimney Pond > summit (several options) > Davis Pond leanto(if you are lucky – it's popular) or Wassataquoik Stream leanto (if you're able to do a 16 mile day and the Park Authority will give you the thumbs up.

Allow 45 minutes drive from Millinocket.

There are other great mountains in the park that are far less popular, so it you can't pull off a 2 day trip around Katahdin there are options. The Namakanta unit of Maine Bureau of Public Lands has a nice overnight loop that gives the flavor of the 100 mile wilderness without the time commitment. See:
http://outdoors.mainetoday.com/hiking/070513hiking.html
and
http://www.maine.gov/cgi-bin/doc/parks/find_one_name.pl?park_id=60