Best bit of advice I was given was - join at the Ploce gate end rather than Pile. There are fewer steep steps to go up in one go, and by the time the crowds have reached the Ploce end they've spread out. I'd heard horror stories about how crowded the walls were; how you'd be pushed along and yelled at for stopping to take pix; how people had been pushed to the ground. I found none of this. You have to be careful with your footing because there are steps, lumps and bumps. There are plenty of places to get photos, and areas of shade as the sun moves round. There are also little craft/souvenir shops and refreshment bars - all at a price, of course, as you're a captive audience. I'd recommend just taking a bottle of water with you. This can be topped up with nice cold water just before you go up onto the wall, from the fountain by St. Blaises church in the old city. Once you join the wall walk, you can't get down and go back up again. The views, both looking outwards from the walls towards the main town or out to sea, and looking inwards towards the orange tiled roofs and little bits of garden, are wonderful. A great experience.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.