Please note, this is not medical advice. This is simply some tips I found to be effective for myself.
1. Stop Chewing Gum
Chewing gum causes your jaw muscles to be overactive and the repetitive movements cause your jaw to become irritated and tight. Chewing gum is one of the worst things you can do if you suffer from TMJ or simply have a tight jaw.
2. Try to break the habit of clenching your jaw or grinding your teeth.
I used to grind my teeth all the time as a kid and it's one of the hardest habits to break because at least for me, I didn't even realize I was doing it. Especially for those people who clench or grind their teeth at night when they're sleeping, it's one of the toughest habits to break.
For those who clench and/or grind at night, I would suggest getting a 'Night Guard'. You can either get one from your dentist or you could buy one on your own, depends how much you want to spend. But they can be helpful. For those of you who clench or grind during the day, try your best to be aware of it. I know it's extremely difficult sometimes to always be mindful, but try...you'll get better over time.
3. Put a Wet Hot Washcloth on your Jaw.
In the evening if you're not doing anything, just watching tv etc, if your jaw feels tight or is bothering you...you can wet a washcloth and put it in the microwave for 30 seconds or so, and put it on your jaw for a few minutes. The heat will help sooth the tight muscles of your jaw. You can also use a heating pad or anything else that you can make safety hot enough.
You can even massage your jaw yourself after putting heat on it with a hot wet washcloth or a heating pad. Simply use your four fingers (not your thumb) and with the finger pads, start massage the area in a circular motion. Under the ear, above the jaw line, even tracing under the cheek bone. Jaw gently massage the whole area...it'll be painful, doing jaw work is usually not very fun, but it can help temporarily make it feel better.
4. Stretch Out Your Jaw
Sounds kinda weird right? How do you stretch your jaw? Well, I'm no expert, I'm sure there's more proper ways of doing it. But for me, I simply open my mouth as wide as I can for a second or two and release by closing your mouth. It also actually helps if you're on an airplane and your ears hurt from the taking off or landing of the plane. The air pressure can hurt my ears, so I would simply open my mouth wide and it would help...yeah it looks a little weird...who cares.
Well, there you go. These are some tips you can do to help your jaw feel better and loosen up a bit. I hope these tips help you. Let me know if you found this helpful.