Olendirk
If you are operating into LHR Then the best advice i can give is to read the notes on your aerads or jeppys before you get anywhere near taking off from your field of origin.
Its no different than any other airport in terms of getting on to the runway except that your more likely to get a hold at busy times. Once on the deck thats when it starts to get busy!
KEEP YOUR XPDR ON, ON THE GROUND until you shut down regardles of what yor sops say or the GMC wont know where you are.
Have the aerodrome and taxy plate out as its a maze on the ground and the point they tell you to taxy to maybe 1/2 a mile away.
Keep a good listen out on the RT and follow thier instructions to a "T".
The LATCC and LHR controlers are amongst the best if not the best and will make it all seem to happen seamlesly.
Enjoy!