What has worked for you?
Brush and floss your teeth daily and visit the dental office for cleaning and polishing twice per year?
^^That may keep your teeth and gums very healthy, and cavities to a minimum, but it isn’t going to make your teeth whiter. Especially if you drink coffee and red wine, and no idiot is going to give that up just for whiter teeth.
I have used the Crest whitening strips with some success. When my husband uses them, his teeth are bright white. Mine whiten up for awhile, and then it’s back to a light shade of yellow again. My hygienist said they basically do just as good a job as the dental trays.
I’ve also used Crest White Strips. Crest makes them in different strengths & ease of use. They all work. The stronger ones just work faster.
The problem for me is the strips make my teeth sensitive, so I can’t tolerate finishing the course. But even after just one application, I can see a difference in the lightening of coffee & red wine stains.
For those with lots of what is euphemistically called “restoration”: Be careful. The whitening products whiten your teeth, but not the fillings/crowns. So you’ll wind up looking mottled.
@GMTplus7 - Have you tried using the strips especially for sensitive teeth or in conjunction with sensitive toothpaste?
@doschicos
I didn’t know “sensitive teeth” packs even existed. I’ll look for them next time.
Does the sensitivity go away when you stop using them?
I have a crown on a front tooth that matched my teeth beautifully 20 years ago when I got it. Unfortunately, coffee and red wine have darkened my teeth faster than the crown and right now the difference in color is very noticable. I either need to whiten my teeth or get a new crown.
Given the price of crowns, worth trying the whitening first.
Yes, the sensitivity does go away after a few days.
To me trays work the best and do all the teeth at the same time. You have them professionally made and then they can last for years. All you do is get refills from your dentist every so often (the gel is stronger and works better than store-bought gel). White Strips do work but they take a long time and usually only go as far as your cuspids (and they are not cheap). If you have restorations in the front teeth that can be replaced, do the whitening first, then change the restorations to match the new shade.
I’ve heard of people applying hydrogen peroxide with a q-tip. If you try this, do NOT swallow.
I just do the strips ad hoc, usually 2-3 days, before an event that’s going to involve a lot of smiling & photos. We always seem to have some unfinished packs in the house.
If you overuse whitening products, it can cause teeth to appear rather translucent as opposed to white. I can’t really do more than an application or two now and then. 
I tried the Target brand white strips with very little change. Next, I tried Crest strips and I did notice a difference, but I still wanted whiter teeth. When I went to the dentist, they recommended Opalescence. I purchased it at the dental office, but I see it is also available on Amazon. It has 15% hydrogen peroxide. The hygienist said that is quite a bit stronger than Crest. It is working well. It is also easier to apply and you leave it on for a shorter time. YMMV
Glyoxide [TM] gel, which contains 10% carbamide peroxide, and is found in the dental care section of stores like CVS , works GREAT, costs FAR less than the strips and has a nice minty taste. 
Using a toothpaste that reduces sensitivity (Sensodyne worked for me), is helpful if you want to bleach your teeth. Also, if using trays, apply just enough to cover the teeth, trying to avoid gums. If you feel tingling in the gums, cleaning them off quickly improves things.
I have custom trays and use 22% bleach as, carefully applied, I can tolerate it. Dentist started me with 16% solution and then we bumped it up. Gets the job done faster. I needed this as I have an expresso machine…
If you wanna spend money, try Express Smile Atlanta’s home whitening kit.
If you wanna save, get some activated charcoal and mix it with some sea salt. Put your regular toothpaste on, and then dab the brush in the powder mix. It will whiten your teeth very well.
After getting a professional whitening, now I use the pre-brushing whitening rinse twice a day. It’s made a huge difference!