Do not use spermicide.
It is basically detergent, and contains some nasties that could seriously irritate the vagina. Not to mention that the way it kills sperm (cide meaning kill, which it does by basically ripping apart the membranes) it can also do to the vagina, causing little abrasions and tears, making you more susceptable to infections.
And, after that, there really is not enough spermicide on condoms to do much good.
Pre-ejaculate can cause pregnancy; it has happened before. While it contains much less sperm than ejaculate does, there is still some present, and it only takes one to cause a pregnancy.
If you want a simple and pretty safe BC, just use a condom for any sexual activity. This means oral sex, manual sex, and so on. Saves the mess and the worries.
[This message has been edited by JamsessionVT (edited 09-12-2005).]