EDIT: Lovely Ben Ward has written an entertaining Hints Guide to Ben There, Dan That! If you're stuck, and want a spoiler-free ish general nudge in the right direction, have a read.
If you've already played the game, it's also worth a read because it's DAMNED funny.
Someone has written a full walkthrough
for BTDT, you can find it here
I haven't had time to read it through and check it myself, yet, but it seems fairly comprehensive.EDIT:
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