To make a good remix, pick a song you enjoy, listen to it carefully and try to find any spots where you would like to add sounds or make other changes. If you are able to come up with good ideas, write them down and decide the order you plan to make those changes to the track.
Pick the song apart, and choose which parts of it you can use in the remix, as some parts that have too much action are difficult to use. Make sure that you are working on the song to improve it and not making it into something completely different.
Some ideas for making a remix are to add a portion of a different song to the song you are working on or to add parts of the original song and plug them into different places in the remix. Artists can also process the stems, for example, by adding parts of the bass stem to the bassline groove. Another way of processing the stems is to make the main melody stem more memorable by adding filtering or phasing to parts of it. Collaborating with other artists to work on remixes can help generate some fresh ideas so you can come up with a high-quality result.
If an artist is creating a remix for someone else, asking the client to provide a deadline for the completion of the remix may help the artist concentrate.