Where to start?

[karindmor]

My son is almost 4 months old and while he's actually not too bad of a sleeper, his schedule is becoming a little more erratic. I think I need to start one with him sooner than later. Can you direct me to the right links to get started please?

[creations]

The first few days of beginning EASY are observation days. So you write down what times LO Eat (time), Activity (length), S (time), and make any notes about if you tried to resettle a nap which was short or if he was in a good/bad mood.
This link has heaps about EASY, you can begin your observation and brush up on the ideas etc
Starting EASY - all you need to know and more!
As your LO is 4 months old you may want to look at the 4hr EASY - this might be why you are seeing a more erratic routine just now, he could need his E times extending, and A times extending to get some good naps in.  I'm not sure if you FF or BF, BF babies (and some FF) do not always make it to 4hr E at 4 months but possibly closer to 6 months, it is possible to extend A times to keep good naps whilst working with a shorter E time if needed.
Time to Transition - 3hr, 3.5hr or 4hr EASY

There is lots of info on the EASY and SLEEP FAQs boards if you have time and want to read up more