If there is alteration that every guy should consider, then it would be hemming the pants. This is generally required when you get accustomed to custom clothing or buying high-quality garments where the pants are usually left unfinished. However, a pant can make or break your entire look. Therefore, if you have bought loose pants, you need to narrow them down. Tapering a pant can certainly be done by a trusted tailor. But before, that put the pants on and know how much you want them to narrow them. You could ask one of your friends to pin them to the right fit.