This is one of the best onpage SEO guides I have ever read online for wordpress (and pretty much for every site).

This article cum guide covers every aspect of onpage SEO from permalinks to image optimization, comment and even conversions using a simplest way.

WordPress SEO Tutorial * The Definitive Guide * Yoast

Read and follow this how-to guide if you need an ultimate site to start with great rankings.

I’d be glad to add if you have more resources to share. Feel free to add them in comments and I will write about them with a credit to you.