How to write PIs asking for PhD position? I have read here that the best way is to keep it simple, be short and ask for meetings, which is a bit generic way to ask for a job. I agree more with the discussion posted here by a student in a similar situation as mine (I still haven't started emailing people but I've already have a long unfinished list).

Speaking with some PhDs and postodcs I know, they told me that the best way is to know somebody in and maybe write them first in order to introduce you to the PI before you send your email. Another advantage of this is that you will know if there is a position available or if it's not a good idea to work there (the people who actually work there might have the best advice about that). Finally, they might also be "more reachable" than the PI who gets thousands of mails. On the other hand, I don't know the people who work where I want to go so it would feel as impersonal as this question feels to you. 

Given the fact that I may have to write several (around 20) of these mails I want to have a good strategy. I know it's a debate that mostly depends on the area. My area of research is Neurobiology of Memory and Learning but I might also be interested to change a little bit, maybe to Addiction (Always within neurobiology).

I would also like to add that in order to write a detailed email about the PI's research history and future path one must be able to have the time for:


Read the publications = A large amount of time 
Actually come out with an idea that meets with the PI's expectations AND research interest/approach/knowledge AND more important technique capacity


Of course, being a PhD student means that you have to suceed in both of them but not for every research we would be happy to do (if we were accepted) in advance.
When drafting your email, keep in mind that PhD advisors get tons of request like this. Your request has to stand out in order to have a chance of success. Most email requests are pretty generic, simply asking for a position, with some generic praise of the advisor's reputation, and a CV attached. 

In order to stand out from the mass, the most important thing is probably that you do your research. What topic is the advisor working on? How does your background fit in there? Make it clear what you think you can contribute to the advisor's work. Try to get all this across as concisely as possible, maybe three or four sentences, at most. By all means, avoid being generic. 

Surely you will have to put some time into it, but it will increase your chances of being considered dramatically. Better to send out fewer but well targeted emails than masses of generic requests. 

If you get no response in spite of your request being well crafted, you can try following up once, after a week or so, but not more often. 

EDIT: "Doing your research" does not mean writing a research proposal, but finding out what the PI works on and putting your skills and interests in this context. Most of the time the info on their website is sufficient, you don't have to read every single one of their papers.