First thing first, you must know what main purpose in using your desired ISP is. Either you use it to play online games, browsing, or even to provide internet connection/send emails for your company you work in.
Please note down also on how many users that will use that connection. If you're going to use it alone (home network) then it shouldn't be much of problem. ISPs nowadays offer broad range of services, from the cheapest one to the most expensive ones for home users. I suggest you to pick based from your budget and availability rate, not from bandwith speed alone. Having a cheap, constant connection service are more important than a fast connection, but expensive and has too many downtimes.
Things are getting complicated if you want to pick ISP for company your work in. You need to choose a provider that offers you the best uptime, ICR, price and availability. You can tell them to make proposal first, and send it to you. After that, make sure you understand the content of their proposal, what they offer to you, what service and what warranty they provide. And most importantly, consider the prices they submit.
After that, you should DO some research. Visit forum or Google it up. Ask for seniors/friends/husband/wife/boss etc opinions. Having more opinions = better. But if you are the decision maker, don't let their opinions influence you, make your decision yourself. Please be aware that here, you can tell other ISPs to make proposals also, and compare each proposals to see which is better!
All in all, be wise and considerate. This is a big bet you play, and small mistake could make a huge difference between failure and success in the future.