They are very addictive so my first bit of advice will be hide your wallet otherwise you will be spending fortunes on Aero bits
Alas my work precludes me from attending the mid week ones unless I book a half day ! but the feeling at the end of your first one is indescribable. I can honestly say it was one of the best things I'd done on a bike.
Here are some slightly better tips:
Most TT's are straight out and back and should have too many corners but a recce of teh course in advance can certainly help.
Warm up! you must go off with warm muscles if it is fairly local ride there (the ride back may hurt a bit though) I rode about 8 miles to my local event which meant I was just getting into my stride at the time of the off.
Try not to go off 1st - Provided you are looking to complete close to 30 mins try and go off somewhere between 5th and 10th. (Have a look at last years results. You should have a vague idea about your expected time and place yourself accordingly) it helps immensly to have someone to chase down and overtake (pride) as well as not being overtaken too often by the fast guys (pride taking a hit), if you go off too near the back.
Do not worry that there are people there on Aero Bikes that sound funny as they whizz by leaving you to stare at their funny shaped lids. They started where you did.
I didn't need a drink on a 10 but we are all different if having or not having a bottle of drink on your ride worries you then take one.
It is your first one once you have popped your TT Cherry you will know how to pace and attack far better and you second time will be better than your first my first was 32 mins my second 29.34.
You should come over the line totally spent but this will take experience (or a bit of luck) do not go off too fast. It will be better that you know you complete it a smidgen faster than limping over the line howling in pain and covered in snot and drool
Actually you should be covered in snot and drool at the end of it. If you are out on the bike the next day make sure you wither have spare gear or have time to wash it.
If it is the perfect weather for a TT never ever say so weather will always be used to account for a slower than normal time.
This is the race of truth it is you vs the clock each time. The only time you should worry about beating is your own - no one elses (unless you are vying for top 3 in your club but then you will be the one offering advice). Do not worry about others times if you can complete a 10 in anything under say 35 - 40 mins you are doing far, far better than most of the UK population could hope to do.
Do not slipstream anyone!
I pulled away in a low gear but in the big ring and tried to keep in the big ring all the time even up the hills however it was a fairly flat course ride in a gear suitable to your course.
Arrive early but not too early to undo the warm up (if you ride there) or early enough to give you 20-30 mins warm up allow at least 10 minutes to sign on get to the start pin your number on.
I will not say enjoy as that will be a foregone conclusion
Good luck - an envious MLC