If a defense attorney has known the juror outside of the courtroom then that juror is not allowed to be involved in the case at all unless a witness or well a simple spectator if the courtroom is open to the public during the trial. If the defense attorney is caught trying to speak a specific juror then he/she most likely will be thrown into jail for contempt of court and possibly jury tampering. There are no techniques that I know of since the jury is a random group of people that have been required to be there for selection by the court. Also I am not positive that the prosecutor(s) and the defense attorney(ies) are allowed to even be present during the selection of the jury. I hope this answered your question somewhat.