Firstly deal with any post that comes in on a daily basis. The trick is to take care of any form of paperwork as soon as you possibly can after it enters the house. The longer you leave it the more time it will take and it could get out of control! Another benefit of dealing with paperwork straight away is that you'll feel much more in control of your finances as you can arrange to pay bills straight away. I used to be terrible and just put things in a pile and then a month later I thought it was about time to sort through my paperwork only to find a bill that was over due. Whoops! Paying your bills early can also save you money sometimes or at least avoid late charges.
Organise and file any paperwork on a weekly basis. If it's out of control and in desperate need of organising, start by sorting into four piles: bills, filing, action and recycling. Deal with any bills that need paying and then file. From your action pile make a to-do-list of what you need to do and endeavour to do a couple of tasks each day. Once your paperwork is under control it will only take you a few minutes each week to sort out.
Another idea is to try and reduce the amount of paperwork that comes in to your house. Firstly, register on the Mail Preference Service as this can probably reduce your mail by at least half. This is where you can choose what sort of mail you do not wish to receive and can therefore reduce the amount of junk mail that comes through your letterbox.
Nowadays, most banks, catalogues and utility services providers give you the option to register online to view your statements and bills. If you do this you can then opt-out of receiving the paper version which will reduce your paperwork dramatically and also be much better for the environment.
Make sure you read the small print very carefully on any forms you fill in and give your details on. Most of the time there will be a small box to tick if you do not want to be added to their mailing list and receive future offers from them or other reputable companies. Be sure to look out for this when doing things online too.
One trick I've found that seems to work is, when you know the item of mail you have received is junk mail and you are not interested in receiving anything from that company, I tend to cross my name and address out and write "Not known at this address, please return to sender" and then post it. I also do this for mail that I get for previous occupants of my address.
Last but not least, another form of mail most of us receive these days is email. Try and check your email every day and deal with it straight away as it soon builds up and can easily get out of control.