Of course sitemap is important for crawling purpose. If you add sitemap Search Engines crawler come to know that how many pages you have in your site.

Well link wheel is the good but for that you will be needed fresh and unique content to get effective results.

well you can also add few more off page activities

Document Sharing
PDF Submission
Micro Blogging

SERP stands for Search Engine Results Pages. Keyword ranking which is shown by Google is known as SERP.