Not to repeat most of what has already been well-said on this thread - but I would emphasize sharing anything that might piss you off during the hunt/trip. We all have our pet peeves and you're shelling out lots of hard-earned money for YOUR hunt.
If sharing the camp with big drinkers is likely to irk you, then tell your PH. If smoking in the field is a no no, then say so - it may not be the PH but one of the trackers. Ditto on cellphones chirping as you're making a final stalk - technology has arrived in most parts of Africa. Your tracker may have a PHD in African fauna but his cellphone is still a novelty for him.
Most operators have this stuff under control but some do not - if you think stuff like this may upset you, then spell it out upfront.
On shooting ability (of which fitness is a key aspect), do your training and practice beforehand. For walk and stalk hunting, anything over 300yds is quite long here. I doubt your PH is going to push you to take shots that long unless he's seen that you can really shoot and it's the last day. If you have genuine limitations on long shots, then share that with your PH. I guarantee he's seen it all, from the best snipers to the worst. He'd rather work a little bit harder getting you closer for the shot than spending 2 days tracking a wounded animal.
If you're unhappy taking a shot, then say so - your PH might mutter about the trophy of a lifetime but he will appreciate not having to track a wounded animal (and you will not regret not having to pay trophy fees for a lost animal)
Also clear up whether you want your PH to shoot in the event of you wounding an animal. And if you do, explain when you're ok with him shooting. You're quite entitled to say no shooting from him and you want to finish it yourself.
Be a sponge and ask your team what they are seeing in the field. Two things you can be sure of - the trackers' skills will blow your mind and two they will be fitter and more agile than you. Admire the first and do your best before the trip in order to push them on the second point
Third point, have fun!