Watch the Standard Tuning Slide: 6 online guitar lesson by Robbie Calvo from SoloCraft
The right hand technique for slide is very similar to that of a fingerpicking style in chordal playing. The main points to remember are that the thumb rests on the strings as do the 1st, 2nd and 3rd fingers muting any unused strings. Please watch the video for visual on what I am talking about here. Selecting the desired string and note with the right hand and muting all the other strings will prevent the slide creating unwanted overtones against the played note. Sometimes those overtones would be sympathetic and produce consonant (pleasing) overtones and sometimes they won't so it is always safer to mute wherever possible.