How to get the maximum download speed?

I think you have a 256 Kbps connection which means you can achieve a maximum speed of 256 Kilo 'bits' per second i.e. 32 Kilo 'Bytes' per second. And you are getting the speed of 25 Kilo Bytes per second (25 KBps) then it is almost OK. You can try some download managers to boost your speed upto 32 KBps.

understand this sivarap.

you have a
256 Kbps - Kilo bits per second
and bits/8 = byte. so 256/8 = 32.
you can get maximum of
32 KBps = Kilo Bytes per second

small b = bits. capital B = byte.

on the topic, how much you receive depends on the server or wherever you are downloading from. if its a HTTP/FTP server then you can get 30-32 easily, because most are fast these days. if not try using a download manager like Flashget or DAP.

if you are talking about torrents, the golden rule of torrents is your download speed is proportional to your upload speed. so when i was using 256 kbps, to get the max download speed, i had a global upload maximum of 5 KBps. i used to get ~30 KBps i suppose. torrent speeds fluctuate a lot, so you cant expect constant 30 KBps.

EDIT:
@debsuvra
damn you got first by seconds

I think what he meant is how to get that 32KBps speed out of his connection. In torrents, it depends on number of seeders u are connected to. U can increase the value in u torrent/preferences/Bit torrent/global maximum number of connection and man number of connected peers. Increase it to some 300 and 200 nd u can fee the difference. And also put maximum priority in u torrent.
And using download accelerators for other servers is gud. Personally opera's dl manager has given me gud speeds. And DAP too is great.

Opera's DL manager is very ineffective. No features at all. DL managers FTW. Also, you can change the TCP Half-Open Connection limit for better speeds. It is 10 on SP2. it can be increased using *www.lvllord.de/ I personally use 1000, you might want to try 100.