OK, where do I start? I hope this bit helps and doesn't put anyone off - it really is so beautiful up past Oxford, it's worth making the trip (if you like the feeling of being in the middle of nowhere!), but life is made even better with a bit of forward planning.
Planning - at least have an idea of where you plan to be at the end of each day. We chose to allow 3 long days to get from Bray to Lechlade and for reasons explained in the blog we still didn't get there. It's OK doing the long days but you need to think about how tiring it can be, where to pick up water and petrol and don't forget you need to empty the pot as well! Use my guide to help plan, I made this 5 years ago and it's in the 'roughly right' level of accuracy - Time and Distance Table
Water - Our Viking tank should hold 120l but it never feels like it is as much as that so we try to top up frequently and we only drink bottled water. We always fill the toilet cistern at the same time (using the shower!). As mentioned, the EA taps are now much slower, you need your own 7m maximum hose and you might encounter queues - so be prepared. I'll add a list of facilities available at each lock at the end of this section. The most important one though has to be Abingdon above the lock - no more EA water points until you get to Eynsham lock which is some way to go (and the most useless tap we tried to use).
Petrol - we started with 70l on board (2 x 25l tanks and a 20l jerry can) which is more than the regulations suggest. We used 115l on the round trip so clearly we had to top up a couple of times. Abingdon is quite good (we picked up 45l here on the way up). The petrol station is just past Waitrose, quite easy to find. Petrol is also available in Lechlade (it's the other side of town though, a bit of a walk). On the way back we picked up 20l from the station in Wallingford which is a short walk. Further downstream from Bray we used to stop at the Bells of Ouzley and Chertsey Bridge to get fuel, handy if you are coming from that far.
Chemical disposal. Abingdon again (Abingdon sounds a bit like Base Camp for this trip!), but also a number of other locks have disposal points (see the list below). We also carry a spare cassette so we can swap over if we don't manage to empty it straight away.
Refuse disposal. Details of refuse points on the list below, it's worth getting rid of a small bag every time you can rather than carrying a huge smelly rubbish bag with you all week!
Sunken boats! Sadly there are still many sunken boats on the river (some have been like it for years) - one to note in particular is in the middle of the stream, on a bend just up from Abingdon! No marker bouys or warnings. Pass on the left going up stream and stay well clear.
Bridges. Obviously many bridges could be hit - but once past Oxford they get much lower and narrower. Osney is low but fairly wide (it also has water spraying from a leaking pipe on the upstream side just to the right of the centre of the arch so something/someone might get wet). But as long as everything is folded down and the river isn't in flood (follow Osney Lock on Twitter to get an idea of river level) you go through no problem. Godstow is probably the worst to get through because it's hard to line up for. Newbridge and Radcot are also a problem in a side breeze or strong current. Make sure things are folded flat, the bow-thruster is armed and that you line up well. If it looks bad, reverse and have another go.
Trees, floating debris and twisty bits. Once past Kings lock the river starts to get quite twisty so forward vision is often limited, this means your pace will be a bit slower. In some places the trees are really over grown and some have fallen. There is plenty of space, but just be aware and keep a good look out - including for floating logs!
Provisions. There's not many easy places to pick up bread and milk once upstream of Oxford. If you moor before Osney Bridge (East Street moorings) there is a Sainsbury's Local not far away, if you are running low on anything this is really your last chance before Lechlade.
Moorings. We know the river quite well and have many spots we particularly like, but when the river is busy places can fill early in the day. On our first day we had hoped for Pangbourne Meadow (which was full) but we knew plan B was Beale Park where I think you'd be very unlucky to not get a spot. Henley has loads of moorings (either on the park town side below Marsh Lock) or on the meadow on the opposite side after the bridge (depending on Henley Regatta of course!). Abingdon has a good number of moorings, Wallingford not bad but not always available. Once past Oxford there are plenty of bank-side moorings available - some a bit more accessible than others, but lots of places to bank the stakes in and enjoy the peace. Also there are moorings at many locks, Kings Lock in particular is a lovely mooring just the other side of Oxford (good for the last night before Godstow and Osney on the return).
Lastly enjoy it, take your time, take lots of photos and make happy memories. I know that sometimes I get stressed about some of the hire boaters who seem incapable of managing the boat, or the people speeding and creating a wash, the inconsiderate moorers who leave half a boat length gap and of course those who haven't mastered lock etiquette (move up on the laybys, move up in the locks to allow more people in!) - yes these things could easily drive you mad but try not to let them, be patient, take your time and relax. A decent bottle of red sometimes helps!
The following information is pinched from the EA (I have it printed out and left on the boat, it comes in handy). I can't vouch that it is correct and up to date! You can also look at Thames Vistor Moorings for more information.