There are not many things in pistol shooting that are more frustrating than a pistol that jams over and over. Don't let anyone tell you that pistol jams just happen and they are something that have to be dealt with. Well designed pistols, most stock pistols on the market today, should never jam.
I have brand name pistols that all have several thousand rounds through them with absolutely zero jams. Some that haven't been cleaned as well as they should have been. If your pistol jams over and over, there is something wrong. Let's find the source(s) of the problem and correct it.
Failure to fire
This situation occurs when there is no visual evidence of a jam, bolt is not open, pistol is in battery, live round in the chamber, and appears ready to fire but when the trigger is activated, the round doesn't fire and a click is heard by the shooter. The chambered round could have evidence of a light primer punch, or no punch all.
How to correct it :
Change ammo - Ammo could be defective due to age, becoming wet, or just a defective primer. If the pistol displays the same symptoms with different ammo go to the next step.
Clean the pistol including the interior of the firing pin mechanism. Gunk build up due to improper cleaning can easily affect the force the firing pin has to strike the primer.
Check the firing pin and spring to insure there has been no breakage on either component. Replace any part this is damaged or worn
Failure to extract
This is when a round fires but the empty case is left in the chamber preventing the next round from being loaded. The action will be open partially and the gun is out of battery. After the mag is removed from the pistol the empty case still will not extract from the chamber with multiple openings / closings of the action.
How to correct
Pry the fired case from the chamber using a small knife of flat head screwdriver.
If the case is split, you may have a batch of poor ammo. Switch to another batch
Clean the chamber and barrel using a chamber brush of the appropriate size.
Check the extractor(s) to make sure there are no excessively worn edges and to insure that the extractor is moving freely. Replace any worn or damaged parts.
Failure to eject
Failure to eject is when an empty case is removed from the chamber, but does not eject from the gun. Usually caused by a worn ejector, low velocity ammo that doesn't provide enough energy to cycle the gun, or poor shooting technique (limp wristing).
How to correct it
Insure quality ammo is being used. Very low velocity pressure ammo can be the cause of this issue as well as a bad lot of standard velocity ammo. Some pistols require higher power ammo than just standard velocity.
Insure proper firm grip on the pistol. Firmness of grip should be about as tight as you hold a hammer while driving a nail. If you had trembles you are gripping too tight. Firm up your wrists and let the pistol do what it will during firing. The stronger the grip, the less movement you will see.
Check the ejector to make sure it is not broken or worn.
Failure to feed
Failure to feed occurs when a new round is not fed into the chamber after the previous casing is ejected. Your slide will be closed but the chamber is empty. A new cartridge was not picked up from the mag. Usually caused by bad, bent or worn mags, low powered ammo, or limp wristing.
How to correct it
Try a different mag. If the problem persists, inspect your mags for bent lips or bullet sticking lower down in the mag.
Change ammo and / or ammo lots
Grip that pistol. The pistol must have some resistance when the shot is fired in order to operate properly
Clean and polish the feed ramp so the bullet can't bind
Look at the tip of the bullet design. i have had flat tip bullets and some really aggressive hollow points that required modifications and/ or cleaning to make them work Never use a bullet in your pistol for self defense without first testing it's ability to cycle through your pistol
A double feed occurs when the pistol cycles, picks up a round from the mag trying to push it in the chamber but there is still a round in the chamber. The causes the pistol to jam with the slide open allowing you to easily see the what happened.
How to correct it
Inspect all magazines for dents or damage that might have change seating height, even very slightly. Eliminate any that cannot be repaired to be dependable.
There are other reasons for pistols to jam including failure of mechanical parts but i can tell you with a brand name quality pistol this happens very infrequently if at all during a pistols life.
I have fired many tens of thousands of rounds through both M&P and Glock pistols without a mechanical or ammo failure.
What to do if these issues happen
All of the jam issues and corrective actions discussed above are issues that should be discovered during practice and the suggested corrections made as permanent fixes well before you are in an intense situation.
There is a method that works virtually every time to quickly correct any of these problems. You must learn it and incorporate it into your practice routine so it becomes automatic.
Here is a video from Warrior Works that does a great job demonstrating this technique.
The tap, rack, bang method demonstrated here works 99% of the time and should be the first step automatically when a jam occurs and you need to get back into the fight quickly.
The only time this will not work is when there is a double feed. Check out the video below on that scenario.
Here is a video created by Storm Mountain Training Center of the methods to use when you have a double feed.
You should practice to immediately go into a tap, rack, bang procedure on any jam. If you still have no bang, go right into the double feed clearing procedure above.
How to best deal with jams
Don't have them. Take the time to proactively prevent jams before they occur through proper cleaning techniques, maintenance of magazine condition, use of good quality ammo, and practice with your pistol. Rimfire ammo runs dirty. Some more than others. It always makes sense to keep your pistol clean.
The time you invest to practice the more likely you will uncover any problems with your pistol or ammo before you really need it to perform.
All of the discussion above deals with semi auto pistols. For many reasons they are the most popular choice today for competition and self defense. But if you don't want to ever have to deal with a jam, there is another alternative. Go to a revolver. You will have far less rounds but a good quality revolver will never jam. The trade off between number of rounds and absolute functionality is a decision that each person has to make for themselves.