Do your sums properly. Double check them all, from scratch.
Mark your route carefully on your chart with permanent marker. Double check it. Also draw some little arrows with the forecast wind speed and direction on the chart around your route, it helps to visualise drift as you rotate the chart during flight.
Rotate the chart as you fly, for the heading you're flying. Keep it real.
Decide on an airspeed and fly it.
Do your best with the wind speeds from the Met Office forecasts. Yes, they're only forecasts and nobody really knows the wind at 2,000 feet, but if you use the data you've got to the best of your ability, you're more likely to end up where you want to be.
Calculate your wind drift corrections carefully and do it a second time, just to be sure. Don't forget the magnetic variation and compass card for your aircraft.
Keep the DI aligned. Check it at least every 15 minutes, more often if you can. Fly an accurate heading, based on your PLOG.
Constantly check ground features, to confirm that you are where you think you should be.
Use recognisable features for your turning points and don't start timing until you've completed the turn and are on your new heading.
If possible, don't start the first leg from your home aerodrome. Use a nearby town/feature that you know already and can reach top of climb before you get to it, as your starting point for the first leg. Do your top of climb FREDA check there, before starting that first leg.
If your calculations say something is 5½ minutes, then it's 5½ minutes. Not 5 and not 6.
Don't rush anything. If you think something is wrong or you're not sure, slow down, fly an orbit or two and have a think about it. Note your timings, so you can resume when you've got it straight in your head.
If you really, really think you are wrong, unsure of position or lost, calm down, slow down, fly an orbit and get help on the radio. They can and will help.
Decide before the flight which ATS units you intend to speak with, which radio nav aids (if any) you intend to use. Note the frequencies for these clearly on your PLOG. Don't bother talking to anyone unless you need to, there is a benefit or unless they call you. Don't feel the need to take a flight information service just because you want to use the radio. It can be distracting and offputting, especially when you've fumbled the radio call, had to say it all twice, noted the response and answered a couple of questions. During which, you've been 20 degrees off track for two minutes.
All of these things work for me but no doubt many more experienced and knowledgeable people will be along shortly to add/detract!
There's something very satisfying about flying a dead reckoning heading for the prescribed number of minutes during training, then finding yourself at exactly the right place, on time!
Have fun.