Over the years I've taken a number of guide trips and have had a number of experiences ranging from outstanding to "I can't wait to get off this boat!"
The personalities of fly fishing guides can definitely be as varied as the species they target. Despite their differences, most (but not all) of the guides I've fished with made it a priority to both be safe and maximize quality fishing time. Something you have to also realize is that there are things you can do as a client to help ensure a smoother day on the water, too. Keeping a few simple tips in mind can make the whole day more enjoyable and productive for all.
1.) Avoid Shoe Disaster: After walking down to the dock, take a few seconds and clean off the bottoms of your shoes. Several guides I've fished with will lay out a big towel to step on before hopping aboard, but if not I'll usually try and dip my soles into the water then stomp a few times to make sure no filth remains. The areas around boat ramps/docks is often wet to some degree, so it's a prime zone for shoes to pick up crud from even a short walk. Jumping aboard a nice clean skiff or worse, a carpeted boat with dirty shoes is a quick way to tick off your guide from the very start! In addition, wear non-marking soles.
2.) Minimize the Crap: I always think like this, but especially on a guide trip I like to bring as little as possible. I try to put all of my items (jacket, snacks, camera, sunscreen, etc) into one small or modestly-sized single storage bag like the incredibly handy and easy to use Simms Dry Creek Dry Bag. I hate clutter, and I like to think most guides don't like it either.
3.) Be Honest About Your Ability: Not the best caster? Rusty double haul? Tell your guide beforehand as most should be happy to give you a bit of instruction on the water. Yeah, it'll likely cut into your actual fishing time a bit, but that's better than frustrating both you and your guide by blowing presentations due to lack of skill. Honestly, I've never understood why some folks book $600 saltwater guide trips but can't cast 20 feet, yet don't seem to mention it or think it'll be a problem. In my opinion, it's always best to hone your skills well BEFORE the trip!
4.) What Time is it: When sight-fishing, your guide will often call out the location of a fish by using both distance and the numbers on a clock face, as in "there's a redfish at 2 o'clock 40 feet moving left." Even if you know your clock numbers well, remember that the clock direction is based off the bow of the boat, not the direction your body is currently facing. Straight off the bow is 12 o'clock, 3 o'clock is directly to the right, and so on.
5.) Be Aware of Your Surroundings: Boats can have a lot of things in the way of your casting—especially flats boats with a poling tower complete with a guide standing on it holding a long push pole. If you spot a fish before your guide, it's easy to get jumpy and attempt a cast at a bad angle or when nobody else is ready. Remember what's behind you, and let the guide quickly reposition the boat for a better angle if you doubt you can get a clean backcast. If casting off the stern of a boat, be real careful not to ping the outboard with a weighted fly. Motor cowlings are expensive and do scratch! Again, casting skill also helps avoid all of these potential screw-ups.
6.) Tippy Boat: On an especially tippy boat, watch the sudden movements. Move slowly, carefully, and as close to centerline as possible. If you need to make a movement that will likely cause the boat to suddenly lean to one side, make an announcement first so that others aboard can prepare and get stabilized. It's not the best idea to cause your guide or partner to take a tumble or get pitched into the drink!