Do a bit of reading on copying. Find a book on the subject. My favourite is called 'copying and duplicating', published by Kodak.

It is not quite as straight forward as it sounds to get really good results. OK results are quite attainable.

The trick to really good is to find a film that gives an upswept H-D curve under a development regime to allow you to get a closer resemblance to reality in the dupe negative. The highlights in most slide films are compressed, and when you dupe using a normal pictorial film, the highlights block up even more by being yet again compresed.

Tech pan was the recommended film. It is out of production and what remains is quite pricey. I have heard that TMax100 developerd in HC-110A might be a good swap for the ability of tech pan, but I have not found the time to test it. Plus X Pan was the next one kodak recommended in thier book. The copy I have pre-dates any of the t-max films.

To suppress the contrast range that slides can present, there is alo a technique called flashing, where by the film is double exposed to a dim white light before or after the main exposure.

Copying/Duping is an interesting side line, but be prepared for challenges before the reuslts are really good.