1) Survive 1st night as you normally would. Get a bit of food/wood/etc.
2) Mine until you get 3 diamonds, make a mining turtle and run the excavate program (or a custom program that's better)
(NOTE: There are better automated mining systems, but this is the cheapest and simplest)
3) Make a renewable energy source (or just pump the nether for lava) and use it to power MFR/Forestry machines to automate all your farming.
4) Somewhere along the way make a mob grinder system. You can use soul shards or MFR to make that easier, but vanilla designs have always worked just fine for me.
At this point you have automated all the major tasks involved in survival, so all that's left is fun projects. My suggestion: pick a mod, look it up in NEI or on a wiki, and try and use as many of the blocks from it as you can. Once you've finished, move on to another mod and repeat. In your next world, you'll know what sorts of projects you enjoy and can skip straight to them.
Honestly starting FTB is a lot like starting vanilla. The only real significant differences are that you can automate mining and automated farming is a lot easier. Depending on your playstyle and familiarity with FTB mods you can get the starting stuff done in a few hours or at least within a few play sessions.
I would recommend getting a smeltery going quickly because TC tools are awesome. Starting on bees pretty early is also nice - it can take a while to breed them up properly. Also a good early investment: Coke Ovens. Coal->Coal Coke is great and all, but with Plugins for Forestry we can turn sugar and cactus into fuel, and those are practically automated for you. Finally, you should visit the Twilight Forest - it's just super cool (also a good source of spawners if you want to fill up soul shards super quick).