Here's an interesting one:
"Quick releases can be very quick."
I see so many newbies who go out and by the most expensive neck/shoulder strap for their camera, WITH A QUICK RELEASE. Then, during a shoot, I see them bump their quick release and ... BANG ... their new camera hits the ground, HARD. Personally, I hate QR straps. I hate straps (neck). If I do use a strap, I attach a small clip cord from the camera to the strap (kinda like a chain on a pocketwatch), especially at weddings where I have little time to watch the strap.
Another cool trick (for MF people). Buy one of those small, cheap LED flashlights, mount an old cold shoe on it (from a busted strobe) and slap it on your camera somewhere. (On my Hassy, it's on the siderail). Works great for focusing in low light without having to use the old videolight on the Stroboframe.
And, for LF people, cheap inkjet transparency sheet (I use color laser ones, but their more expensive, and clearer) work great for marking your shot with info. I do this so I can remember exactly what I saw when I shot. (using a grease pencil). I lay it over the GG and mark away, including any logistics that I see on why the image was layed out as it is. In the darkroom, I just overlay the sheet on my neg and it helps me see what I was after during the initial shot.
For those wedding/event shooters who shoot with Metz 45CT/CL strobes or similar...if you want a cheap backup battery (or don't want to pay for Quantum batteries, go to Radio Sh*t and buy some of the "RC car connector repair kits" (23-445) and a bunch of cheap RC car 9.6v battery packs. Pop apart a bad battery connector and solder a coiled cord to the correct contacts, attach the RC connector to the other end, get a cheap belt pouch and you have extended power! I built one for mine, about $50.00 and I can get almost 12 hours of shooting out of it!
Finally, there is the old string with loop at one end and 1/4-20 or 3/8 screw at the other end instead of a monopod. I've used this setup to shoot down to 2 sec (at Getty Museum in LA) with my HB and no monopod to carry. (Insert loop around foot, screw into camera, lift camera against foot and press into forehead or eye)