Many people do some research online before making purchases. This usually also includes attempting to find the place where whatever they intend to buy will cost is cheapest. Good it is for saving money but it can also be a great way to fight impulse buying. If you can make it a habit to do some research before buying something then you wouldn't buy something which you haven't been planning to buy because you don't know if you are or aren't getting the best deal.
I do a moderate research when buying phones just to see if the phone has no issues and the ones who have used it are happy with it. I do that also witn books, I want to know if it's worth buying or not before I actually buy it.
The time of research depends on the amount of the item. For appliances like water dispenser of gas stove, it takes about a month or two for the data gathering, asking around. When we were prospecting for a new car, it took us more than a year to make a final decision before buying our Ford Escape in January of 2013. We made a long list of cars with features and prices. For smaller items like kitchen wares, no need for research since they are not that expensive.
I always check the price on another site and reviews, then I check ebates or quidco to see if they are listed so I can get an extra rebate. Otherwise I will do a search for a coupon code and see the best option. I rarely impulse buy unless it's something very cheap, or I know it's a bargain at the price.
If the item will be a big purchase like a laptop or a new phone then I will do extensive research prior, but otherwise I'd maybe just spend a few hours looking around for a good range of the price to see if I'm getting a good deal or not. It I'm buying at a physical store then I'm less likely to research it first which is why these days I usually just stick to buying cheap items like plain shirts whenever I'm shopping at a mall. However, if I'm at a mall and I'm buying something a little more expensive like shoes, I'll maybe hold off until I check around online to see if I can get it for cheaper.
I research hardcore lol. I'm the Google Queen, so I always always find the cheapest possible item out there and that's how I choose where to buy as well. Not before also researching every review ever written on the item as well. Unless it's something super cheap, of course.
Like some of the other posters, it usually depends on how expensive the item is. If it's an electronic that just came out, I like waiting for everyone else to buy it first. That way I have time to read reviews and compare it. I'm not real tech savvy and I don't mind not having the latest techy stuff.
With beauty products, I do thorough research before buying them. Because usually, what the bloggers say about products is the true description of it. I won't even bother buying a certain new lipstick without researching first, how long it lasts, its ingredients and its pigmentation. With clothes, I sometimes just buy impulsively when I find something I like. But to be honest, I don't have much problems with clothing items because I'm quite picky about them.
I always spend some time to do a research, compare prices and find reviews before buying. But the final decision depends on the strenght of my wish to own the item. It works mostly fine for me