The London School of Economics is one of the most over subscribed higher education institutions in all of the UK, and hence is fiercely competitive.
Here is a 4 part breakdown as to what needs to be done to give you a fighting chance for an offer at LSE (with a slant towards applying to Economics, but can be interpreted to the subject you want to apply to at LSE also.).
1) Your GCSE results, these need to be of the highest standard.
As mentioned here, in how important are GCSEs to the London School of Economics, the majority of your GCSEs need to be either an A* or an A.
There have been many numbers flown about as to how many A*s etc. but the norm would probably be nearing on all A*s at GCSE.
Don't let this put you off applying though, as if you read the article above, they do take numerous factors into consideration.
They will also take into account the type of subjects that you took at GCSE also.
2) Your Personal Statement
LSE dedicate quite a lot of information to telling you what they want from their personal statements.
It is obviously a crucial component to them for differentiating their candidates as they don't interview their candidates.
They give you literally a list of key features that you should take away and incorporate into your personal statement - things like 'indicate an awareness of what Economics involves' so they obviously want to provide evidence to show you are aware of what Economics is about.
I would also recommend you check out the seven book economics reading list for before writing your Economics personal statement here.
(It would also be a very good idea to check out the article 'How to Get Into LSE' - ten useful points to consider when writing up your personal statement.)
3) Choosing Your A Levels
I have come up with what I consider to be a strong combination of A levels to apply for Economics here.
The London School of Economics once published a sort of black list which listed the A levels that were less preferred.
Hence this definitely shows there lies a preference to the sort of A Levels you apply with, so make sure you have done sufficient research into what LSE requires A levels wise and what A Levels LSE likes.
3.5) Obviously, you also have to apply with incredibly good AS level more than likely aaaaa (if you are following the plan that I set in choosing your A levels for Economics) along with high A2 predictions (make sure you are at least predicted their minimum entry requirement).
I would also get it mentioned in your reference if you have particularly high UMS marks in your AS levels.
4) Have Great Extra curricular Activities
They can show the selectors the evidence they are looking for.
"Selectors are also looking for evidence of interest and an understanding of the course you have applied for."
Whilst acting as a way to differentiate yourself from the crowd, for some ideas on how to do this click here.
Although aimed at Economics, many of the ideas can be used for other subjects also.
Such as setting up the Economics blog can easily be setting up an Geography blog for example.
Good Luck and don't get too disheartened with the amount of competition, it is at least worth applying, besides it is only one of your five choices.