How to use Margin, and be smart about it ?

I have been doing stocks for 15+ years but i never used margin at all because i dont like the chance to lose it all (for the same reason i dont use options at all either) Right now my portfolio is 85 % equities (single stocks only) and 15 % cash. Would it be smart to use margin, how much and how does it work specifically using IKBR ? thanks,