There really isn't any truly safe point. Ovulation can occur at any time in your menstrual cycle, and young women frequently have particularly unpredictable cycles.
Some couples do use a method of contraception called fertility awareness, but it is not recommended for young couples, given the reasons I mentioned above. It also requires very careful charting of the woman's menstrual cycle and several other factors, and even when done very carefully, there is still always a pregnancy risk.
If you wish to have sex without using condoms, your best approach is to obtain some form of hormonal birth control such as oral contraceptives. Keep in mind, however, that homonal birth control offers no protection from STDs and STIs.
These articles may be helpful:
Safe, Sound & Sexy ? A Safer Sex How-To
What's The Risk? - Five Easy Risk Assessment Flow Charts
Margaret Sangers Disneyland - An easy chart of your birth control options
Testing, Testing?A Quickie STD/STI Risk Assessment
"The only unnatural sexual act is that which you cannot perform."
-- Alfred Kinsey
[This message has been edited by kythryne (edited 04-11-2002).]