The first thing to compare will be bandwidth and disk space. The key point to remember is that disk space costs a host very little whereas bandwidth is quite expensive. So if host A offers you 20gb of bandwidth and 100 megabytes of disk space and host B offers you 500 megabytes of disk space and 15gb of bandwidth Host A is making the better offer.
The next step is to ask the hosts to show you some sites that they are already hosting. You are asking to see these so that you can see the speed that the site opens at. Too slow and you should not use them. It is advisable to check these sites several times during the day as some servers get very busy throughout working hours but quiet for the rest of the time