Cut out the vocals from songs. For this purpose, special programs that are available, for example, the website listed below the article. Insert track vocals each in a separate file, preferably in the format .waw or similar, preserving high sound quality.
Draw a diagram of the instrumental accompaniment, consider how "cut" the vocals to create new melodies and rhythms. Make sure that the song evolved from simple to complex: tools should be added gradually. Conformed with the style of the Remix: reggae, tango, jazz, electro etc.
Make turns all parts on all instruments in the track in this order: drums, bass, rest of the rhythm section, Yes. Last, insert the track with the vocals and treat in accordance with their needs.
Keep track: get overtones, balance the volume of each track adjust the frequency. In the final stage, add effects. Save the file in format .mp3 or .waw depending on the purpose.