Not many I’m afraid.
Broadband speed is primarily controlled by your Internet Service Provider (ISP), and there’s little that can be done to improve it on your end.
There aren’t really any changes to your computer that you can make, but here’s a few tips to ensure that you get the best possible speed:
1) Make sure that your broadband router is connected to the primary phone socket in your house. Connecting it to a secondary socket will increase the signal loss, which will cause speeds to drop.
2) Make sure there are ADSL filters on all sockets in your home. Not having these will more likely kill your Internet connection all together, but it could cause you to get slower speeds than you could get.
3) Check with your ISP to see if they have a download limit. Sometimes they will restrict your speed if you download heavily during peak times in order to ensure other customers get fair speeds. If they do, try scheduling any large downloads for during the night, where you’ll get better speeds anyway.
If none of these steps work, try contacting your ISP and asking them to do a line test on your telephone line. This will check how good the cable from the local exchange to your home is and could show any issues which are preventing you from getting the best speeds.
In the worst cases, it’s not unheard of for your supplier to replace the line, if it’s deemed that a poor quality line is causing you a problem.