Newbie

Welcome, nice outfit. As you won't find it too easy to park it off sites chose your sites carefully so they are near public transport and think about getting alternative means of transport .e.g. bikes. If you haven't got one already, get yourselve a sat nav to help you avoid low bridges and unsuitable roads. Make sure it is one which lets you define your motorhome size and weight and preferred roads.

peedee

Big motorhome. Plan your routes. Have a look at site directions online. Have a look at google street view for the last mile. Never trust a Satnav 100%, always read the road signs. 

Remember at slow speeds your rear end will pivot out on you rear wheels and you can’t see that in your mirrors. There are some good YouTube tutorials mainly based on American RVs but still good.

if you have a passenger on board get them out to direct you when reversing, and watch for tree branches or overhead obstacles that don’t apply to a car.

in terms of ‘what to look out for’, think what tools you need to take for breakdown or repair and have a security plan.

As you are over 3500Kg, I presume you have the requisite categories on your driving licence.