Part of the reason why a phone screening is such a good evaluation tool is that it only requires you and the candidate to set aside 30 minutes to an hour to speak. Time investment and scheduling difficulties are minimal.

Contact the candidate well in advance to set up a time to speak. Many candidates will prefer to use Skype or Google Hangouts to conduct phone screening, depending on their schedule. Be flexible and understand that some candidates will be scheduling interviews around their normal workday responsibilities.

For an engineering candidate, you ought to be covering fairly technical concepts during the interview. If you are an HR representative and don't have technical expertise, you'll likely be asking questions on behalf of a more technical manager, which may be difficult. If it's possible for your company, you might split the phone screen into a non-technical phone screen, which you conduct, and a technical screen, which engineering employees conduct...