What's the Ideal percentage to contribute towards 401k to earn maximum benefits?

If your are younger than 60 yrs old, you can contribute up to 18000, that will be non taxable now, over 60 you can contribute up to $ 24000.

If I were your financial planner , without knowing your Income level, your tax liability , mandatory expenses and tentative saving , it will not be easy to advise .

before going into detail and to keep long story short.....contribute only what the company match.
if company does not match...go with Roth IRA.