The first thing to ask is what you want to use the tablet for. That will tell you what screen size you need, whether it needs pen support (though very few have that), whether it needs cellular data connectivity (which adds to the cost) or just WiFi. Once you know that, see what's available within your budget and, as zuben says, go and have a play with the real thing if you can, or at least have a look at a few. Don't be fooled by ultra-cheap devices that claim great specs: there will be a reason they are so cheap.