1. You don't get 'spill over' rep at exalted from most quests in starting zones, so do the zones in order.
2. Human diplomacy 10% bonus
also applies to the spill over rep and makes a huge difference.
3. Check out what rep is converted to what when you faction change here :
World of Warcraft Community Site
4. Gnomeregan is considered by most to be the hardest / slowest
5. Use wowhead quests for the zone you're in, turn the map on with quest giver locations. There's a nice quest tracking addon you can use to keep a track of what you've done but I can't remember the name of it. I couldn't find anything that queried your completed quests from server, the addon only started tracking what I'd done AFTER I installed it.
6. Check the wowhead FACTION quest lists too to double check the quests you're doing reward rep, especially in the belf areas where you can waste a lot of time doing quests that only give ghostlands rep.
If you do it right, you'll hit ambassador just after you start quests on the last faction. For me I started tauren, did everything horde, faction changed to human, worked thru the races one by one, and spent an hour or two doing night elf quests when I got the title.
I know of friends who did zones in the wrong order, missing out on 1000's of spillover rep who still got it no problem so don't keep too close an eye on the rep bars or worry too much, if you do everything you will get title with room to spare
ps. good to see you back Peni