If you simply want to remove hinges etc, fill a glass bowl half full with tepid water - room temperature - not too cold but not hot. Place the stamps into the bowl and make sure they are submerged to get wet. If you are doing multiple stamps, make sure they aren't stuck together - Don't overload your bowl - if you are doing lots of stamp (I never do more than about 50 at a time), I use the kitchen sink (after making sure its clean). Don't rush the process- the biggest mistake most collectors make is they try to get all the paper off after soaking for a few minutes - if its something as simple as hinges, they'll come off in a couple of minutes, but stamps on fully backed old parcel paper might need a couple of hours of soaking - and be wary, occasionally stamps are affixed with glue that is not water solvent.
If the stamp is grubby or the paper backing looks really stuck on, use slightly warmer water, and add 1 to 2 drops of unscented dishwashing liquid soap per gallon of water - and let the stamp soak for several hours - do not tamper with the stamp - but I occasionally stir the water gently to create some movement - this will often be enough to loosen any backing that is no longer glued but just barely hanging onto the stamp. On occasion, I have left a stamp to soak this way overnight. If you use the dishwashing soap, you have to transfer the stamp to a second bath of pure clean water and leave it for 30-60 minutes to remove the soap from the stamp.
Stamps soaked for a long time are more fragile than ones that only get a few minutes in the water, so make sure you have good tongs, and work with surgeon's care. I usually disturb the water a bit so the stamp floats in the water - you don't want to try to scrape a stamp from the bottom of the glass bowl - get it moving and then pluck it from the water when its positioned properly for easy access.
I use a dishtowel spread flatly on the kitchen counter for the first drying surface. Place the stamp flat and face down onto the dishtowel and let it stand for 10-30 minutes. With the backside up, you can see if there is any residual gum on the stamp - sometimes you just have to leave the excess glue (some of these glues don't soak off very easily), but you have to be sure its dry, or your stamp will get stuck when you move to the next step.
Once the surface of the paper appears dry (no standing water, or "glistening" look), carefully lift it from the towel with tweezers and place it between 2 sheets of blotting paper, and put a flat book on them with a bit of weight. Leave it for a couple of hours. If the stamp is stuck onto the blotting paper when you try to retrieve it, do not force it - if it has re-glued itself to the paper, you have to cut it out and resoak for a minute or two and it will release, then dry it and press it again - especially if its a rare and valuable stamp. Once it comes out of the blotting paper, I put the stamps into a Hagner sheet and press again for 12-24 hours. This gives them that crisp, flat look that makes them look like premium stamps.
I have done this with $5000 stamps - but must admit I'm nervous every time I do it. Handling wet stamps requires care and patience to insure you dont crimp them or tear them - but the end result is worth it . I've had stamps that brightened 2 shades and look fresh and clean after looking grubby and dull. And those hinge bits can often make stamps have a curled look even when mounted - once they are soaked and pressed, they will lie flat. Try it on some common stamps first - its amazing how much value you can add to a stamp with a simple bath.