Please explain the plan and why you think its best.
The best option is the employer sponsored plan – these are the 401k, 403b, SIMPLE IRAs, etc. You contribute out of your paycheck in pre-tax dollars, which reduces your tax bite every paycheck and goes directly into a retirement fund. Your employer may match your contributions, so for every dollar you put in, they will give you a percentage "match" and that’s free money.
Next, Roth IRA (if you qualify) this allows you to save money post-tax for retirement (and soemtimes you can withdraw early for specific reasons, like education, hardship, buying your first home). Your savings grow tax free and when you withdraw, the distributions are tax free (in most cases) after 59 1/2.
Next Traditional IRA, similar to Roth IRA, but your distributions are taxed at your then tax rate rather than your now tax rate. Most people are in a lower tax bracket in retirement, so you allow your savings to grow tax free and distributions are taxable at your tax rate when you withdraw.
IRA contribution limits for 2007 are $4,000 if you’re under 50 years old and $5000 if you’re 50 or older. Then, taxable savings.
As an afterthought, you may consider annuities, insurance and long term care, but these are usually not recommended unless you have maxed out your other tax advantaged retirement accounts or have very specific concerns.