Nails are quite a complex jump after basic production, so you're going to have to be prepared to do some work to get to the point where you can make them easily. The two most important things you're go to need to be able to do are:
After you have mastered these skills and are able to produce Iron and Charcoal, you'll need access to a Student's Forge equipped with a Nail Mould. Many public buildings exist; you likely will not have to build one of your own.
You will get 24 nails for each deben of Iron you use in the Student's Forge. You'll need 10 Charcoal to make the forge light, and to make enough nails for your tent. Pay close attention to the forge; your fire will go out if you run out of charcoal before you finish your project. It's best to take a few extra charcoal, just in case.
You are also welcome to trade for nails, many players are willing to do so. Check Trade Lists or chat up your neighbors, friends and guildmates.
If you would like to build your own Student's Forge and equip it with a Nail Mould (for those solo'ers and ambitious ones amoung you), you will need to complete the following steps.