When addressing a patient requesting emergency or post-coital contraception, a focused, non-judgemental history can direct both you and the patient towards making an agreeable decision about clinical management. This is also an excellent time to review sexual risk factors, and build a solid rapport so that, should the patient be faced with a pregnancy, she will contact you quickly, reducing the potential for a second-trimester procedure.
Details regarding sexual encounter
Type of intercourse (oral, vaginal, anal, voluntary, involuntary)
Was contraception used?
If so, was there an obvious contraceptive failure? (missed pill, condom slippage/breakage, ejaculation prior to withdrawal)
Delay in seeking emergency contraception
Day 0-3 (72 hours) - most effective interval for Emergency Oral Contraception
Day 3-5 - an IUD may be inserted at this point.
Menstrual history - This will help you to stratify the risk of pregnancy, but should NOT change your clinical management
Last Normal Menstrual Period
Are periods regular?
Always Ask About Abuse 
"In general, how would you describe your relationship: a lot of tension, some tension, no tension?"
"Do you and your partner work out arguments: with great difficulty, some difficulty, no difficulty?"
Remember: Risk of conception = Risk of STI
For women: Last Pap Smear? What was the result?
For women and men: Offer to conduct STI testing (including HIV, for which explicit consent is needed)
Validate and address any additional concerns the patient has.