Well, an interesting question and the answer depends on a number of factors. The most important factor is any liability I may have, especially in terms of education loan or car loan or credit card bills. The first priority is to get rid of all the loan since the interest rates are fairly steep. However, I would try to put away as much money as possible every month (after taking care of my liabilities).
At the very least , I would like to invest 20-25% of my paycheck every month. An early start is always useful in investing, since it provides a longer time frame and is aided by power of compounding (returns are compounded). And I would hope that this investment is apart from my 401 (k) contribution.
My classmates would have their own opinions on this. Some may have much higher loans and credit card bills than I do or other liabilities (mortgage, etc.). Some of them may be saving for short-term goals such as marriage or further education or a new car/truck. I would say that, in comparison to my peers, 20-25% savings is a pretty good number and would put in the top investing echelon among my peers.
hope this helps.