Ever had an issue with your server being down? How about needing to cancel the server? There is an endless list of reasons why you need to contact your host. So, where do you go to get them? This should provide some basic insight!
Member Section / Billing Suite: This is likely the preferred method of support for your host. This is where you'll submit a support ticket, find help paying your bill, and update your account profile and billing information. One of the most commonly used billing suites is ClientExec (found
here). This provides the host a way to log your conversations, keep everything on file, have access to all of your information, and manage the account. As a benefit to you, this also allows
all members of support to see and assist with your ticket, not just the one on one conversations on a livechat, mIRC, etc.
mIRC (Internet Relay Chat) One of the most common means for support and contacting Game Server Providers, mIRC has become a staple for anyone in the gaming world. I'd suggest having it and using it if you've got just a basic support question, or need to speak with someone pre-sale. Grab it
here.
Email The good old fashioned way to contact your host. Again, should be used for basic support or sales questions, but a very efficient way to get them. Most companies will be support@(company) or sales@(company), so it shouldn't be very hard to get them!
LiveChat Tons of companies these days have LiveChat clients built right into their site, most which update and tell you whether or not a support or sales member is available. Give it a shot!
AIM/MSN/XFire Most hosts have instant messenger support available as well. This should be reserved for quick questions though, don't want to annoy them too much
Forums! Check out the companies forums, are they active? When was the last post? How competent and professional are the posts by the admins/staff? You can get a lot of information about a company, and their servers in general, just by looking at what people have to say. You can also post asking for help there, too

.
As you can see, there is certainly no shortage of ways to get a hold of your host. You should never have to complain about never getting support again.
-brian