well right now I am on shared hosting and I feels that because of many other accounts the speed is slow as the site don't load that fast. Is there any way I can check it how "(over)loaded" the server is ? what should be considered the good loading speed ? like in xx Kb/s
bandwidth is not normally what slows things down, it's the hardware resources being used up. if you have shell access or sometimes access to a control panel you should be able to get system load statistics. if you have shell access, login with ssh and type "top." the numbers depend on the hardware. if you have one CPU, below 1.0 is ideal. two, 2.0, etc.
well I don't have a shell access but using reverse IP I can see 171 sites on it which I feels is a little too much as some of them are proxiy sites and game sites. Let me see what can I do with cpanel..By the way, I do have a whm account, can this help me in some way ?
yep ! whm is perfect. you can see the load average there. look for "system status." get the load average as well as the number of cpus. having whm access on shared hosting is... very odd, though. the number of sites doesn't mean much. sometimes you can have 2,000 sites on a box, othertimes with identical hardware you can only host a site or two. the far majority of websites use almost no resources.