Advice/Tips for first time racers I have entered a 30km mtb race that will take place in a couple of weeks time. I don't know much about the route and won't be able to get on it beforehand as it goes through private farms that will only be opened for the public during the race.

The profile is as follows:



Does anyone have any tips as far as what a good average speed would be, what a good average time would be and when or when not to go all out? Sprint in the beginning? Sprint in the end?

Any tips would be greatly appreciated.
Don't make any major mechanical changes to your bike the day before the race. If it ain't broke, don't fix it- at least not at the last minute. You will end up kicking yourself for it. Make sure you've had plenty of riding time on your bike's current configuration.
Bring tools and tubes, but pack light. Bring a small/medium sized multi tool, a tube, something to air it up with (preferably co2), tire levers if they're not part of your multi tool, and maybe a patch kit if you have bad luck with flats.
At the gun, go for the hole shot. Most mtb races will start in an open area and give you somewhere around a quarter mile to a couple of miles before singletrack to vie for position. Ending up middle or back of the pack means a lot of clawing your way past slower riders throughout the race which equals lots of lost time. Sprint early and then slowly let off to recover. Don't be the jerk that gets the hole shot then blows up only to be passed by the entire field.
Find your pace and settle in. After the sprint start it's important you recover and don't over pace yourself for the rest of the race. Otherwise you'll find yourself blowing up before the race is over. 
Drink before you're thirsty, eat before you're hungry. Words to live by when riding regardless of whether you're racing or not, but especially important when you're racing. Bonking and cramping sucks, so be proactive in avoiding both problems Bring plenty of food and water. Gels are preferable as they're easy to consume when you're running near redline.
Be polite when passing and being passed. When you need to pass, let the person ahead know your intentions and which side you plan to pass on, and wait for a safe place to pass. If someone is asking to pass you and you're not in podium position, let them by at your earliest convenience. Don't let impatience or pride get in your way in either case.
Don't wear headphones, even if the race organizers allow them, unless you plan on leading from the gun to the finish. Don't be that guy. You'll know what I mean the first time you try to pass someone who's jamming out instead of paying attention to the race.
Don't sandbag. This one is for your second race if you blow the field away in your first race. Bump up a class if you embarrassed the competition, because it's shameful to stay in a class just because it's an easy win. Not saying this is you but it's worth getting out there for others.