Disclaimer: I'm a complete novice to investment, so please adjust the style of your answer accordingly.

There are some good questions on this site about "what percentage of my portfolio should I keep for X?" for things like [stocks](https://money.stackexchange.com/questions/10439/what-percentage-of-my-portfolio-should-be-in-individual-stocks) and [gold](https://money.stackexchange.com/questions/8474/is-there-a-general-guideline-for-what-percentage-of-a-portfolio-should-be-in-gol?rq=1). While those are good, specific answers, I'm looking for a generalization: how do I balance risk vs. diversity vs. ROI vs. whatever and figure out what percentage of my portfolio should be allocated to which investments?

My personal profile is to go for steady, long-term growth. I assume, therefore, that riskier investments should be a smaller percentage of my overall portfolio. I don't know how much smaller though; should I confine it to only 10-15%? Should it be at most, half of my baseline/normal investments?