I love challenges.  Life is way too boring without them.  However, there are times I really wish the photo-gods and light all lined up to perfection.  

Photographing weddings is probably the biggest challenge I have ever taken on.  One I also never take lightly.  I have photographed 4 star Generals and still find weddings more challenging.  The biggest challenge is the lighting.  Most times we as photographers can only control the light to a minimal extent.  We can set up off camera flash units which help tremendously.  It is just that some venues, honestly most, don't take into consideration the photography end of a wedding.  

I just finished a lovely reception at a location that drove me crazy.  Bright light on one spot of the dance floor and the dungeon of doom on the other side.  Thankfully my new assistant is very tall guy.  He held the OCF on the stand over my head most of the night.  I ended up just turning off my on camera flash. There was nowhere to bounce it and as dark as this place was the last thing I needed was blast-o-flash or the total drop off of flash output from diffusers.  And catching focus.  That was truly a challenge.  It got to the point that I was able to, most times, anticipate the next movement and set up focus early.  

In situations like this one really needs 3 OCF setups.  I don't know if that isn't just a bit too intrusive.  Guess I will just have to try it.  So if you run into a situation such as this my suggestion is get your iso up on a good camera, set your shutter speed around 60-100 depending on how steady you handhold the camera, go wide angle and get the flash off your camera!  Know your camera buttons, their functions and where they are by touch.  You will need to constantly make changes throughout the reception.  The light changes constantly, especially in a poorly designed lighting system.  Watch your aperture.  If you shoot wide open your dof is going to be rough because with a wide angle lens you will find yourself very up close and personal, shrinking your dof greatly.  And I have found at least with Canon L-Series lenses that the 24mm really is at it's best less than 12' from the subject.  It is it's sharpest.  Shoot it with a pro-level full frame and it gets even sharper. 

So don't be totally blown away with badly lit venues.  Just improvise.  That's why it is so vitally important that you know your camera and the basics light and color theory.  They truly come into play with poor lighting.