Talk out loud about everything you're doing... all your Freda checks and the little things like switching the fuel pump off after 1000ft, switching the fuel pump on whilst changing tanks, updating ETA's etc etc.
Nav --> Expect a diversion somewhere along the second leg of your flight, my advice would be to keep your map/chart and pen or chinagraph pencil to hand, so you are ready when issued with the diversion instruction. Try and pinpoint you position on your chart, then draw a line free hand from your position to your diversion point. You should then be able to reasonably estimate the true heading by eye, don't forget variation and you'll have to estimate drift. For estimating distance quickly on a 1:500,000 chart, on the average adult, from the tip of the thumb to the first knuckle is approximately 10nm. Also, I used 90kts for my average groundspeed (PA28), which meant time would be 2/3 distance. So a diversion of 30nm would take approximately 20 minutes. Hope that makes sense.
I found this useful... better than fumbling around for a scale ruler and such like whilst trying to fly the aeroplane. Remember you are allowed to update your ETA, just make sure you tell the examiner.
PFL --> A PFL may interupt the flight at anytime so try and be constantly on the look out for an appropriate field etc, but don't let it effect your flying. The examiner may well pick a field for you, each examiner is different. Again, my advice would be to talk about everything you'd do.." Airspeed... Trim... Mayday Call... Why has it failed... Carb Heat... Fuel Pump... Change Tanks... Restart... Tighten Safety Belts... Open Door" etc etc. Also.. .after going around from the PFL some examiners like to be real b*stards and give you an 'Engine Failiure after take off', so be prepared!
Bad Weather Circuit --> Bit of a weird one this, a lot of schools don't teach this to students (well they didn't teach me until I insisted on it)... make sure you're more than comfortable with this, some examiners (older ones especially, me included) think that this is a very important... some others think that it is dangerous.. so whether you get one or not is anyones guess... but get it nailed anyway just in case.
Circuits --> If you've not done many circuits recently due to doing solo Nav and such like, I'd recommend going doing a few... all types really... Normal Powered Approach, Glide Approach, Flapless Approach and the above bad weather circuit too... you may well be asked to perform all of these.
Stalling --> Also may have been a while since you covered stalling, so make sure you are comfortable with that as well. One I find always catches people out is Stalling in a turn... remember... pitch the nose to the horizon... no lower
full smooth power
Anyway, thats my 2p, hope it is of some use to you, overall best advice from me would be just try and relax, do as you have been taught... and above all use your common sense