I refer most people who ask to Dilbert's 9-Point Plan, which Scott Adams originally published in 2002 but has been reproduced many times all over the Internet eg
https://retirementplans.vanguard.com/VGApp/pe/PubVgiNews?Art...
If you can't click through, here's the list:
Everything you need to know about financial planning
1. Make a will.
2. Pay off your credit cards.
3. Get term life insurance if you have a family to support.
4. Fund your 401(k) to the maximum.
5. Fund your IRA to the maximum.
6. Buy a house if you want to live in a house and you can afford it.
7. Put six months’ expenses in a money market fund.
8. Take whatever money is left over and invest 70% in a stock index fund and 30% in a bond fund through any discount broker and never touch it until retirement.
9. If any of this confuses you, or you have something special going on (retirement, college planning, tax issues) hire a fee-based financial planner, not one who charges a percentage of your portfolio.
"What to invest in" is only answered in #8, which you shouldn't even think about until you've worked through the previous 7 steps. Yes, write that damn will already!