Help me increase my downloading speed

Hello,
I have a 256Kbps Broadband connection which gives me downloading speed of 32KBps
one day it increased to 300KBps for some time....my computer got hanged becoz of some reason so I restarted it ,unfortunetly the speed gone then. Since then I never seen that speed. I don't know how it occured but I want it again.
I have DSL 4.5 and SG TCP optimizer softwares but I don't know how to use then with best possible settings.
Please tell me What i can do to get that speed again and tell me the best settings for that softwares.
Or suggest something else tweak or software!