I need help about changing my description and title meta tags, is it ok if i change my title and description meta tags even if my sites is already been index by the spider and is it ok to change my anchor text when making link trades and directory submissions? also like to ask if when does my cached page be updated? or does search engine updating it?
you can change your meta tags with most appropiate title and deccription, actually you should. regarding anchor text for link building, it depends on how many backlinks you have with your current anchor text and how many you need to get ranked for your niche. when you change anchor text, don;t use something completely different, use an anchor text that has similar word relationship
if my site rank 50 in google for a certain keyword if i update my title tag and description tag and my keyword tag targeting my anchor text and the keyword that rank 50 in google will it help my rankings?
It is okey to change title and description at any point of time. Make sure you submit your site to www.google.com/addurl/ saying that you have changed title/description. It is vital to use variation in anchor text. Yes, search engine do update cached pages. But don't bother about it.