It doesn't have to be in a volcano. Mine isn't.
PRESENTING: BLITZERLAND'S GUIDE TO SECRET LAIRS
Let us start with the basics.
1.) Choose a location that no one will think of searching. Several locations could be:
A- Under your house
B- Under the ocean (bring snorkels...maybe rent some air)
C- Within someone else's lair (always effective)
D- Somewhere so obvious, no one will look (inside Lincoln Memorial, perhaps?)
2.) Make sure your lair is effectively camo-ed.
A- Cover it with grass clippings
B- Bury it
C- Post a sign declaring "free used beer" near your lair
D- Print this page out, shred it, use peices to cover lair
E- Put a huge rock on top of it
3.) Equip your lair with all the necessary stockings. You'll need:
A- Lethal weapons
B- A laboratory
C- A home theater (a quiet one, so people don't hear you playing "Matrix" at full blast)
D- A bedroom (duh)
E- A cool looking room where you can throw gigantic parties with your lackeys
F- Whatever else i've left out
4.) Recruit lackeys. Look for people with the following traits:
A- Gullible
B- Loyal
C- Stupid and worthless (you'll need comedy relief)
D- Knows CPR (if you choke on spittle while laughing demonically)
E- Strong
5.) You'll require a way of defending your lair if attacked. Try:
A- Littering the area with plasma mines (be careful getting to lair)
B- Sprinkle defense cats around your lair (careful...rates are high nowadays)
C- Play "Cher" at full blast, all the time (you'll need ear plugs)
D- Bribe goverment (they need money nowadays)
E- Hire mercs (can be expensive, if at all possible, do step F instead)
F- Train lackeys in self-defense
END