Regarding link velocity -- yes it matters. Everything you do try to make it look natural. Certainly you don't want to have no links for 2 weeks, then 1000 links in a couple days, then no links for weeks thereafter.
I usually only backlink a page when I think it needs a boost. Lets say it's settled in firmly at #24 and hasn't budged in 2 weeks. I've done all the internal backlinking to that page that I expect to do -- and Google has had a chance to evaluate those internal backlinks and even so ... its still stuck at #24.
Thats when I know it needs some help. I'll backlink to that page -- either using exact anchor text (which I do around 20% of the time) or I'll do "click here" or something similar, with the exact match keyword right next to the "click here".
Then I'll move on to the next page on the site, auditing it seeing if it needs a backlink. I give Google a chance to reevaluate the rank of that website and I will probably revisit the page in a week to see if it has improved.
The link will come in the form of a high PR blog post, or a web2.0 post. I know I have to elaborate on how I do these more, and I will very soon write huge posts dedicated to these two.
Again with social signals, I do it slow and steady with my own accounts. Only dozens of likes/google+/retweets ... not hundreds. Feel free to go with more if you have experience with it and you know its ok.
I also link to the homepage, probably 1/5th of all incoming links I do are to homepage.
AWESOME POST! I always wanted to ask this though: People always talk about backlinking and where to get links from and all. However:
1) What do you think about velocity? Is it a big factor here?
2) And I've been dying to ask this: how do you backlink for every page? For example, if we're talking Web 2.0s, do you like, make one web 2.0 for every article and then go for second tier? I mean you have the options. Blog networks, social bookmarks, web 2.0s, high pr blog posts...etc. How do you distribute those options on your homepage and internal pages?
Thanks!