Getting a faster internet connection always helps in boosting your download speeds, however for those of us on slower connections, there is still some hope.
Tweak your manager
We'll use Free Download Manager (FDM) as our example. Go to Options > Network, set Traffic usage mode to Heavy Mode. Increase the maximum number of connections and maximum number of connections per server. Also increase the maximum number of mirrors. Remember to tick the "Automatically search for mirror URLs" option. If you use Windows XP and Orbit Download manager, go to Tools> Preferences > Others and check the "Increase connection limit for Windows XPSP2".
Speed up torrents
Before you start downloading from the torrent network, check your maximum upload speed settings using online speed tests. Set your client's upload rate to about eighty per cent of your maximum upload speed. For μtorrent Go to Preferences > Bandwidth and change the "Global Upload Rate". Use queuing and connection settings to download not more than two torrents at a time.
Use browser extensions
Using browser extensions for downloads certainly reduces your time. As you don't have to crunch through a number of steps before you start your downloads. Use "Down Them All" for Firefox, its developers boast that it increases download speeds by 400 per cent, but we would not necessarily go that far. It does a pretty good job though. Secondly, to grab any kind of media content currently playing in your browser use the "Download Helper" extension for Firefox to automatically catch it and download the file. Also try Download Master extension for Chrome. Activating Grab++ option in Orbit Download Manager also catches any viral video or flash files playing in your browser.
If you are downloading a file at a peak time when there is a lot of traffic, then you might get inconsistent or slow speeds, for this try downloading the file at different times of the day. The lower number of people on the network will mean better speeds for you. This is especially important for system admins in offices, who should set downloads for the night, when the bandwidth is freed up. Use queuing to ensure that no more than 2 downloads are running concurrently. Also clear your browser cache often, and help your PC get some much needed RAM back.