I have seen alot of people round here going nowhere fast with picking keywords for adsense sites and coming up against some big players so I thought I would give some tips if you are looking to rank a site easy and monetize it. For this example I want you to forget adsense, it can be hard starting out and I haven't even mastered it yet. Instead look into sites that offer services like cleaning, plumbing, builders, painters and all the trades, there are loads of them. If you think locally for example "cleaner london", and then break it down to smaller groups "cleaner westminister" you will find that the competition gets halfed. This is just an example. You could have a site londoncleaning.com and then all the suburbs like londoncleaning.com/westminister and then try and rank that page for the keyterm "westminister cleaning". To rank for a service/location is dead is easy and when you rank well for a few you can start to sell advertsing space to business'. Obviously London is going to be hard but there are thousands of searches in places with no competition and it will take you a week to rank for them with hardly any work at all. This could turn out to be alot more profitable than adsense, all you would need to do is create a simple directory and stick a paypal button on your site and collect money. I saw a site doing this recently and it was pulling in over £40,000 a year and it was all automated selling £10 adds for 6 months. Before you jump in to adsense think about other ways that you can exploit your advertising.
Theres alot of money in services, plumbing for example is a big industry and they will pay for advertising. For a plumber to have a decent add in the thomson local it will cost £2500+ I do have a services site but I have set this up for someone (a services business), the traffic is better when you target loads of sub areas, you might only have 30 UV's a day from one area but when you rank for 100+ search terms the traffic starts to add up...