a.) What are things to look for if your site ranking goes down in Google listing? ( i.e. I have lost the top spot, what happened?)
A: Most obvious reason would be a drop in backlinks. Obviously when you are not aggressively acquiring new inbound links to your site on a day-to-day basis, existing backlinks may even deteriorate in value or The referring site may disappear, be changed, lose relevance or lose PR itself, reducing the PR that is passed onto you. Thus resulting in dip of your listing.

b.) Should I submit my website to Google every month?
A: No, you only need to do it once. In most cases you will not even need to submit your website to Google. If you are active in building links to your website then Googlebot will frequent your site soon, and thus include it in the index.

c.) My site is not cached in Google, I’ve submitted it to google numerous times but I’m not seeing it crawl my entire site. I’m also seeing an incomplete listing.
A: Sometimes the googlebot will visit, and leave, only to come back at a later time in order to crawl all of your pages. If a site has no cache, or an incomplete listing, it has not been crawled and indexed properly yet. The best thing you can do is get more in bound links to your site, so that the googlebot arrives to your site from more than 1 source.

d.) When I look up my site in Google, I am #23, but when some in Sanjose looks it up I am #31. Which one is right?
A: They both are! Actually, a more accurate explanation is that Google using multiple datacenters that deliver the results you see. The datacenter that is used depends on your geographical location. It is very common to see a small difference in results depending where you are. Sometimes, results can differ when you move just a few miles away!