Before starting with my job hunt, I also knew that most of the ads on these sites are placed by recruiters acting on behalf of the company where the vacancy exists. Further to my knowledge was the fact that contract jobs are available in a vast number and are much more rewarding purely on financial terms than permanent jobs. Yet, there were quite a few things which were a complete surprise for me:
Tip #1: Add "keywords" to your CVRecruiters run queries on your CV! This is something that I have deduced based on how recruiters have contacted me in the last one month. They always demand "MS Word" files for CV's, which clearly indicates that they run some kind of tool on these CV's. Now, all job sites can "import MS Word CV's" and can automatically pick out "education", "projects", "skills" and "job history" from your CV---no matter how you have written your CV. Of course, sometimes this parsing is not 100% correct but its amazingly close to perfection.
Now, recruiters are not programmers or project managers though they have specializations in hiring certain kind of people. I believe that most of them import your CV in their system, see a job spec for which they are hiring and run a query on their system for matching keywords. No keywords, no match and thus, no call.
The conclusion is that for starting your job hunt in the UK, make sure that your CV is "query optimized" and not just looks pretty when printed. For a developer/ manager, some important keywords for the UK (other than core programming skills are): agile, test driven development, unit testing, scrum, xp, etc.
Further tips will follow suit.