I've played Dragon Mountain (we lost

) so I reckon I can offer some decent advice here...
1) Re: high level characters. Don't let them have the full wealth available for players of their level, or at the least, pick some of their items for them. Players that can choose that level of money often end up with overpowered, maxed out characters, simply because it makes sense! So be careful.
2) Maybe run them through a preliminary adventure so they can get the hang of their tactics before venturing on to the meat of the campaign. Nothing worse than seeing 2 hours of character generation go down the pan.
3) Re: DM itself. I didn't like the preliminary stuff, all the finding of the Amulet. I would suggest doing something else to get it into their hands, or failing that losing it entirely. Although the hordes-of-kobolds-attacking-a-small-village section sounds like fun.
4) Inside the mountain: DO NOT let the characters rest unless they find a very secure area. DM should be a nightmare for them. Hassle them with kobolds in the night. Stop the spellcasters from resting. Have them giggling in the walls ALL THE TIME. Your players will hate you, but they'll remember the session.
5) Your worst nightmare is if the players realise that the kobolds are nothing but a distraction and simply run through and on to the Dragon. Keep them occupied. Make them hate the kobolds, and want to kill them. That way the Dragon has plenty of time to learn about them and ready itself. Bwahahahahaha!
6) Don't be afraid to pull kobold tactics. Overbearing, mass grappling, hit and run into tiny tunnels, the works. Make them annoying.
7) As mentioned, depending on what level the characters are, make sure some kobolds are higher level to give the party a 1 on 1 threat.
8) Mass spellcasting. 30 kobold adepts casting
silence and hold person is more of a nightmare than you can possibly imagine.
9) Make the dragon sneaky. We had a kobold
polymorphed into a dragon first. I blew it away with a lightning bolt, thus blowing our cover entirely...
10) Enjoy it! It's a great module!