And, later regret not handing it over to the agency (now knowing exactly what they charge the commission for!).
Find out as much as possible about the place, lifestyle, weather, transport, certain peculiarities you would like to experience; all this before leaving, so you are equally well prepared for the happening and not-so-happening moments.
In fact, if you are really looking forward to 'relaxing', you should choose less crowded places and enjoy your way (basically avoid those long waiting lines for something like a 'light and sound show').
You may wanna pack the luggage accordingly; that includes not just medicines, but something like medical history. Also, keep enough time to waste/spare a day or half so that they can take a break.
Let each one choose how he/she wants to go around the place, and probably meet up for lunch or dinner somewhere later on. You might even end up going to the same places at the same time, and like it that way.
Give your boss or colleagues a plan for your absence, and accordingly finish your pending tasks before you leave. Decide when, if you must be in contact with them, and keep it minimum. Remember why you're on a vacation!
Try seeping in the ways of the destination, and don't go upset at how bland the food tastes. Expect less and try finding fun in the moments you live away from routine.
Get in touch with what you missed out on. Discuss with your colleagues about what happened in the meanwhile. And, go a little slow with yourself initially, for a faster and productive comeback.