I just recently hit max crafting skill level so here's what I find useful.
All crafting is done at Memory Alpha. There are research and development stations placed in the large central chamber as well as many of the smaller rooms that can be used to craft items. Just walk up to any of these stations (they can be simultaneously used by any number of players) and hit "F" to bring up the crafting interface. The interface itself is pretty easy to understand. It lists all the items you can craft, the quantity of each raw material required to craft the item and the minimum skill level required to craft the item. To craft an item, you just have to make sure you have enough raw materials and skill level. Simply select the item you want to craft and hit the "Fabricate" button. Most items require a two-step crafting process where you first craft a schematic, then use the schematic to craft the actual item.
You will need lots and lots of data samples that are collected from scanning anomalies or from doing certain duty officer assignments. The best way to gather these samples is to go to a star cluster, half the "uncharted" waypoints are anomalies just waiting to be scanned so just fly around scanning every anomaly you can find. You can get about 300-400 samples in just under an hour of scanning.
Crafted items are split into roughly 8 tiers of difficulty where each tier offers equipment suitable for at a specific starfleet rank. For example, tier 1 goes from crafting skill 0 to roughly 240 and offers gear that can be used by Ensigns, tier 2 goes from about 240 to 470 and provides gear suitable for Lieutenant characters, so on and so forth.
On average, crafting an item will gain you anywhere from 10 to 50 crafting skill, depending on difficulty level of the item being crafted. So on average you'll gain 30 crafting skill points with every item you craft. This means that you can easily gain max crafting skill level of 1650 ( any EQ crafters notice this?
) by crafting 50-60 items.
However bear in mind that at about Commander level, some of the more powerful items will require you to spend dilithium to buy either common or uncommon unreplicable materials.