Some tips:
1) When In Doubt: NEI. When you bring up your inventory screen, you'll see a new overlay. This is NEI, and it is used to track recipes, and has some very useful integration with crafting in general. When your question is 'how do I make x', your answer can be found in NEI. You can search by name, you can also click on an item to see how it is made, and press 'u' while hovering over an item to find out how it is made. When you have opened a crafting table (or most other crafting interfaces), you can bring up a recipe in NEI, then press Shift + the ? button and it will automatically populate the recipe for you!
2) You probably started with a book in your inventory (unless you are playing Unhinged). READ IT. This is the start of a mod called 'Tinkers Construct', and it is made of win. It completely revolutionizes your tool crafting, repairing, and augmenting. I consider it to be in every way superior to vanilla tool crafting. You'll need a Stencil Table to make the patterns, a Part Builder to bring the patterns and the materials together to make the tool pieces, and finally, the Tool Station, which is where the tools themselves are crafted, named, repaired, and modified. The moment you make one of these, you'll get a new book, telling you the ins and outs of tool manufacturing and modifying. Cooking up Grout will net you Seared Bricks. Four of them in a square nets you a Seared Brick block, and a third book which will tell you how to make your Smeltery (needed for any tools made with metal parts), how to upgrade your Tool Station to a Tool Forge, and some information on alloys.
3) There's several magical mods and several technological mods out there. It's best to find a guide or a Let's Play or something when starting fresh on one of them. In general, for tech mods, you're going to need something that makes power, then machines that use power, and some form of transmitting that power from the something that makes the power to the machines that use it. You can also see what machines can make and what they require to make it in NEI as well.
4) Many mods include new 'worldgen' or new things that appear in the world for you to harvest and use. For example, you are likely to encounter Copper and Tin ores in the world. If you aren't sure what it is, then bag it and figure it out when you get back to base and you have the luxury of browsing NEI at length. Trying to navigate NEI while in possibly hostile territory is not recommended.
5) Don't Panic! All the vanilla minecraft stuff still works, so if you don't want to dive into the deep end, you can start off normally and ease your way into the mods.