Assume that you've used my advice and found a warranty with all the desired characteristics. Follow these steps to greatly increase your chances of having a good warranty experience.
Take the product home and set it up right away. Use it as much as you can in the first week or two to find any true "defects". If you find any, take it back to the store and get a replacement.
Most stores give you 30 days to exchange a defective product, but it can be as little as 14 days depending on the product. If they try to charge you a "restocking fee", remind them that you're not returning the product, but exchanging it.
Also note that this will not work for open/used/display items, only new.
After this period, watch for any performance issues and note them until you can find time to take it to the store.
You did make sure that the plan covers performance, starts immediately vs. after the manufuacturer warranty, and that you can bring it to the store during the entire warranty period, right?
Take it to the store and drop it off. Be sure to remove anything such as memory cards, batteries, cables, removeable drives or anything else that can be take off without using a screwdriver.
If you need/want to send such items with the product, make sure that they are specifically mentioned in the paperwork the technician gives you before you sign it.
They should ask you what the problem is with it when they start the service order. Give them a list of everything that you noted wasn't working well. There are two reasons to do this: One is that you really want them to fix everything. The other is that you're hoping they can't fix it all and have to replace it.
When the product comes back, test it immediately (if you can) and look to see that all the problems have been fixed. If not, give it back to them and tell them to try again.
Make sure that you get paperwork from the first time you sent it in and verify that they are not considering this an extension of the previous repair, but a new repair that counts toward the no-lemon policy.
Assuming that, at some point, they are either unable to repair a problem, or they've hit the limit of repairs under their no lemon policy (you have to count them, they usually won't), tell them that you want to have it replaced under their no-lemon clause.
Be prepared with a list of features from your first product and bold the ones that are important to you. If the replacement takes place several years after the purchase, your product won't likely be available anymore and they'll try to substitute a current item.
This almost always works in your favor since the technology will have progressed and the new item will nearly always have better/more features than your last.Don't let them shortsell you!Whatever product they show you for replacement, make sure that it has all the features that were important to you from your last one. Try the display model and see how well it works. Have the salesperson explain why they picked this model over any of the others.
If the product is unacceptable in some way, tell them what it's lacking and make them show you something else. If nothing is suitable, they will have to give you a voucher for the original purchase price of your item (assuming you made sure to get a good warranty). Then you can buy a lessor product and pocket the difference or upgrade to something better (while paying the difference).
Note that "unacceptable" does not count brand or price. Unless you can demonstrate that the replacement offer is lacking in some significant feature, you will likely have to accept it. A less that favorite brand, a color you don't like, or a menu system that you're not used to won't typically count.