My advice:
Deploy mooring lines and fenders both sides in plenty of time. have LOTS and LOTS of fenders especially in the summer.
Have mooring lines which stay on the pontoon if possible.
If possible have a mooring cleat midships (this I believe is how commercial boatman tie up when first coming alongside)
Think hard about the effect of the wind and the current on the boat
All lines have to be run back to the cockpit (in some situations tie the two ends together with a loose reef knot)
A short line amidships is sometimes useful with a large eye spliced in the free end for dropping over a convenient pontoon cleat.
Some means of escaping the helm is essential so have some way of locking the tiller in position.
...or get onto Ch80 and ask one of the marina staff for a hand. I've always found them to be very co-operative.
<hr width=100% size=1><A target="_blank" HREF=http://www.stingo.co.uk>http://www.stingo.co.uk</A> <font color=blue>- still showing at a computer near you</font color=blue>
All 1st class advice - but why more fenders in the summer?! Doesn't the warm weather make plastic boats more pliable and soft so they bounce harmlessly?!
A good trick for single-handed mooring is to rig a short spring from your midship cleat. Hook this over a cleat on the pontoon/boat you are going alongside and then motor ahead gently to hold the boat alongside. From the helm you can then adjust the engine speed and lock the helm to hold her in position. Hop ashore with your lines, tie them at leisure and then you can stop the engine. Works for me!
I also have a variation where the bight of the spring goes through the midships fairlead and back to the cockpit outside all the rails. One end is made fast to the midship cleat, the other end comes back along the deck to the cockpit. From the cockpit I can drop the bight over a cleat or bollard and then take up the slack, cleat it off in the cockpit and go ahead as before.
When single-handed, I take a line from a midships cleat in a large loop back to a sheet winch. Having come alongside, you can easily flick this over a cleat on the pontoon and you are secure. If being blown off, you can use the engine and the winch to pull yourself in. If you want to try again, you can easily slip it from the cockpit. This works well on finger pontoons as you can catch the outside cleat and be sure that the bow is well clear of the main pontoon.
It is also worth having normal bow and sten lines ready to pass ashore though. Whenever people have offered to take this single line, I end up confusing them trying to explain what to do with it!
If I have another person onboard, they step off with a short warp on a midships cleat. Once this is made off, you can motor against it and are in complete control again from the cockpit.
I agree with 'arran' give yourself time. Preparation is everything! reseach ahead where your going what are you like to expect when you get there. Have lines and fender ready, both sides, maybe so you have time to see and plan whats ahead and dont have to swap over. And dont be frightened to abort (preplanned) and try again. It may will be a good to practical anyway if the winds strong or gasty.
And ask for help, usually when your seen to be on your own you dont have to ask.