Tip # 1 :
Do NOT stuff keywords into your image Alt tag. Use the Alt tag only for describing what the image is. Keywords in the Alt tag do NOT influence relevency at all. It is important to use every tag for the purpose it was meant to be used.
Tip # 2 :
Include a link to your site map on every page of your Web site. Many search engine robots look for your sitemap in order to crawl the entire Web site. If you include a link to your sitemap on each page, you are giving the robots easy access to crawl your entire Web site, regardless of which page they come in on.