Hi, My site is @ #3 for a long time. Now I wanna push it to #1. What happen if I add link to my signatures in some forums I participated in, then get some tons of backlinks in a very short time? Will this be good or bad to my SERP?
Adding signatures to forums is - in my view - a helpful thing. From what I've read, don't get an unnaturally large amount of backlinks at once - build up in a "natural" pattern. Also, vary the anchor text.
Sig links certainly help but as jj1 says, a deluge of links all of a sudden would look spammy to the SEs. Personally I think it's better to build higher quality relevant links than vast quantities of low-grade ones.
From what I've experienced, sig links mostly give you visitors. Backlinks from blogs, other websites etc. improve your SERP. You could combine these two of course. Increase the amount of links you build gradually and use different anchor text as said above.
If you will get in the short time a lot of links, there will be a problem. -If the site is new -If you use the same anchor text -If you backlink only to domain level -If you use same domains and which are linked together ...... This is not a natural way, its not good and you will lost the rank and possible get a ban.
Forum and directory backlinks, and nowadays blog backlinks are being downgraded in importantce by Google. Once decent inbound link from a quality website is worth a 1000 forum signatures! A consistent link velocity will aid your site and keep you free of the scrutiny of the big G.
Pushing from #3 to #1 even for moderate keyword might take effort because #1 and #2 sites are probably also optimizing their sites continuously. You need to try link baits, guest posts etc. Simply forum links won't be able to help much.
It depends on if it is in the thousands or not. I recommend less than a thousand daily and not in bursts since this imitates linkfarms.