Wht is the minimum percentage I have to start withdrawing at 70?

Starting in April of the year after you reach age 70-1/2 you have to take a minimum withdrawal amount as determined by the IRS. Depending on your age and the ages(s) and of your beneficiary(ies), there is an assumed number of years that you (or your benficiary) will be withdrawing funds - so you divide the amount in your account by that number of years. For someone age 70 whose sole benfecary is a spouse whose age is within 10 years of the account owner, the distribution period is assumed to be 27.4 years, so that year you must take a minimum distributions of 1/27.4 = 3.65%. Here's the table: IRA minimum distributions table

UPDATE - I think the "Worker, Retiree, and Employer Recovery Act of 2008" waived the requirement for mandatory distributions for 2009. So if you turned 70-1/2 in 2009, you may not be required to take a distribution by April 1, 2010. You should contact your IRA custodian and ask about this.

If someone who has contributed to 401 plan and has been on the job for 30 years passes away, can next of kin withdraw?

It depends on whether the "next of kin" is the benficiary of the 401(k) plan or not. Almost all 401(k) plan particiapants identify a beneficiary (or beneficiaries) who would inherit the 401(k) upon death of the participant. In general the answer is yes - the beneficiary can take withdrawals, but the details of how that happens varies by plan, and be aware that income taxes will be owed on any withdrawal (but not a 10% early withdrawal penalty). There are different options available depending on whether the beneficiary is the person's spouse or not. So best thing is to get in touch with the plan administrator and ask what the rules are. Also I suggest you read the following web page - there is some really good information about how inheriting a 401(k) works:

401khelpcenter.com - What You Need to Know When You Inherit a 401k