Did you remove the barrel? I read that on some newer models the barrel will bind up with the recoil spring guide rod and has to be loosened a little to get it together.
There's not really a trick to it...basically, practice makes perfect, and it really depends on what year yours was made. The pre 2001 type (with the solid steel slid is way easier than the post-2001 type with the plastic insert inside the hollowed out slide. This is one of those things that is way hard to describe in typed words than to show in person.
The first video that DaverZ posted shows it pretty good at about the 3:00 mark.
Sandra, check your messages. I sent you a PM with my email. PM me your email and I'll send you a 14 page guide to dissecting the Buck Mark. It covers both the old and new slides.
Peg
**EDIT**Here is the web page of the guy that wrote the PDF guide.
http://chim.embarqspace.com/#/page-12/4529737053These photos go well beyond what is required for dis-assembly for routine cleaning, but it helps to see how the gun goes together.
I have one completely apart in a box at the moment. It belongs to friend that went to the
Michael Bane School of Gunsmithing.

He "polished" the inner surfaces, trying to get a better trigger, and now the hammer/sear won't engage each other. I'm probably going to have to order all new innards from Brownells to get it working again.