In Cairo, for example, a hotel room for three would end up being less expensive than three hostel beds, yet you would be sleeping on a king size bed in your own private room. They can help you decide which one is worth staying at. Otherwise, you may show up to find that the hostel you wanted to stay at is full up. if you are walking to your intended hostel and you run into a friendly group of people who are going to a different hostel, join them if you feel welcome to. try to arrive at a hostel earlier in the day to get a good bed and avoid being bumped. Some hostels close in the middle of the day for cleaning, but you can still book a room and drop your stuff off. Kitchens usually have basic cooking utensils and pots, pans, and dishes.
Some hostels have safety deposit boxes for smaller things like cameras.
Otherwise, take your bag with you. If you plan on staying out until late in the night, you may come back to your hostel to find yourself locked out. If you do arrive late, respect your roommates and keep the noise to a minimum and the lights off. You can make one easily by folding a sheet in half and sewing it up one side. Keep about half a meter un-sewn at the top so you can fold it back a little when inside.