London is huge. People like me who have lived here quite a while pretend we know it. We don't. It's just huge. There are 580 towns of which people like me know kind of roughly where 200 of them are after ten years. For this reason, there are 'classic' flatsharing and rental areas and the most famous of these are Islington,Hackney, Shoreditch, Kensington and Clapham, but there are 100 other towns that are popular. You can make a much more constructive search on MoveFlat by using the search menu which you have to click on to open from the home page.
A good place to start with this is to search along a tube line that your place of work is near.Also be aware that because London is an old city, it isn't defined by a grid and the borders of areas can get a bit vague. This vagueness is ruthlessly exploited. The famous example of this is Islington which is a town and a borough. The purists regard Islington as the area around Angel and King's Cross. Advertisers can put Islington as much as two miles from this.
In general however think a little wider than the area where your freinds have gone to live or it is considered desirable to live. This will not necessarily suit you as well. Also be aware of areas that are emerging as popular rental places and their transport links. You could save some money and convenience to boot.