Update Regularly, this is very important for SEO. The search engines know how old your site is and how often you update it, by constantly adding content to your website and building links, over time the search engine will notice the natural building of authority your website is gathering. Once Google can see your site is in fact being updated regularly and is is slowly increasing in the size of it's original quality resource, they will rank you higher for the subject of your site, creating a profitable web site with a good stream of visitors from search engine is not just about your SEO efforts but about how much quality you provide for your readers and how much they use and like your web site. If you have a blog, post often, if you have a site thats already built, then continue to write relevant articles and hubs etc pointing back to the site and refresh the look of the site often. Always look after your site and keep it updated and the Search Engines will thank you for your efforts. Good Luck with your SEO efforts but remember a good site is a good start!. People will tell you to worry about header tags and meta tags and HTML and all that jazz it can help a little but it's mostly rubbish. The search engines job is to find the best sites for a specific query, keep this in mind and you will always out rank your competition that is wasting their time with SEO tricks instead of creating a good quality online presence.
I update my blogs twice a month, is that ok... I don't have much time to update my blog more focus on my sites to push through...
I try at least once a day but it depends a little on your niches. Just try and think about what the search engines are going to notice you or your competition that posts just as well but daily? But if your content is unique well written and above the standard of your competition you willalso do well, and remember to backlink to your posts!!