I have heard from some anglers that once they have a  plactic worm/hedge hog/fluke start ripping they just toss that in the tackle box and later on melt them down so that they can be reused again. One way to make a lure last...

But what is the best way to do this?

You can use a "melting pot" or a microwave oven.

I use a pyrex measuring cup and microwave to melt them down.

Do you mean you melt down the plastic all the way and then you remold? That would seem like a lot of work....

Yep I melt them down to a liquid them repour them.

Ok my method seems a lot less work than melting them all the way down but we'll see. If the lure is not to destroyed I simply hold a lighter underneath the hole and it melts quickly and seals the hole right up.

It's not much work once you have all the necessary molds. Handpours are the way to go for plastics. One thing you have to watch out for is if you over heat or heat the plastic to fast it will scorth and smoke. Go slow and have fun

I save mine and repair or modify them with a hot knife.  It works good for smaller to mod. tears and holes.  They make a worm welder that operates off of batteries.  There is a link about one made just a few days ago on here.  Once they get to a certain point remelting is the only option.

I repair some plastics by holding them over a candle and sealing the holes. I used to pour some baits and also remelted some to be repoured. However, remelting usually resulted in a degradation of color. But black was perfect for remelting because the color stays the same and black has always been one of my favorite colors anyways.