For a person attempting to capitalize on the Reagan tax cuts under The Economic Recovery Act of 1981, it helps 1) to be in a high tax bracket, 2) to be well off enough to have a significant amount of discretionary income and savings and 3) to have income other than salary that can be manipulated for tax purposes.

In simpler terms, it helps to be rich.

For the very small percentage of the population with high "unearned" income from dividends and investments, for example, there are relatively clear tax strategies. As of Jan. 1, 1982, the top rate on such income exceeding $215,400 on a joint return will drop from 70 percent to 50 percent, the single largest tax break for individuals in the legislation.

For persons in that category, along with many others facing top marginal rates above 50 percent, a consistent tactic suggested by tax advisers is to postpone, whenever possible, income from 1981 to 1982 to take advantage of the lower rate.

Conversely, deductions, which reduce tax liabilities, should be accelerated from 1982 back to this year whenever possible in order to reduce taxable income while the 70 percent rate still holds.

These basic ground rules also apply to persons with taxable income below the 50 percent rate, but to a far less significant extent. Rates for everyone will be cut by 10 percent on July 1, 1982.

For taxpayers filing joint returns in the $29,900 to $35,200 range, however, this will mean a top marginal rate cut from 37 percent to 33 percent from 1981 to 1982, or 4 percentage points. This break will disappear if the taxpayers' income grows next year into the next tax bracket (above $35,200), where the rate in 1982 will be 39 percent.

In contrast, the top marginal rate on all unearned income above $215,400 will drop from 70 percent to 50 percent. For unearned income between $162,400 and $215,400, the rate will drop by 18 percentage points, from 68 percent to 50 percent.

Touche Ross and Co. suggests that an executive in a tax bracket above 50 percent consider postponing receipt of a bonus until 1982. Another tactic the firm suggests would be "to invest in Treasury bills with maturities in 1982. . . . There will not be any income recognition on the portion of the discount 'earned' in 1981 until it is collected at maturity in 1982. The same result can be achieved using six-month money market certificates issued by banks and savings and loans." The owner of a closely held business could postpone income by delaying payment of dividends until after the close of the year.

On the deduction side of the coin, Arthur Young and Co. recommends that persons in the very high brackets consider prepayment of property and state or local income taxes, speeded-up medical or dental work so that it is paid for in 1981 and fulfillment of charitable pledges before the end of the year. All these actions would lower tax liability at a time when the maximum rate on unearned income is still 70 percent.

The radical drop in top tax rates on unearned income makes investments in tax loss shelters more advantageous this year, although next year, when the top rates drop, they will become less attractive. Arthur Andersen and Co. notes that "because of business tax cuts effective this year, there may be time to generate losses and tax credits based upon partnership investments in 1981."

For persons in a position to save money, the 1981 tax bill offers a number of new options with varying degrees of attractiveness.

One proposal that went into effect on Oct. 1 is the All Savers certificate. Lending institutions can issue the one-year certificates, which pay tax-free interest at a rate set at 70 percent of the rate for the most recently issued one-year Treasury bills. The current interest rate on the certificates is 10.77 percent, although it will change monthly as new Treasury bills are issued.

The certificates are advantageous only for persons whose taxable income on a joint return is at least 30 percent, or about $30,000 a year in 1982. For those with incomes below this level, the net after-tax income would be larger from a direct investment in Treasury bills. No matter what the taxpayers' bracket, the certificates are a better investment than keeping money in a passbook savings account.

In the higher brackets the incentive to invest in the certificates increases sharply. For a taxpayer in the 50 percent bracket, a 12 percent tax-free return is the equivalent of a 24 percent rate of return on a taxable investment.

A person considering the certificates must, however, be prepared to give up the use of the money for a full year. In order to qualify for the maximum lifetime exclusion of $2,000 for a joint return, a couple would have to invest about $16,500. Redeeming any portion of a certificate before maturity makes the interest income subject to taxation. The certificates are available in denominations of $500.

At the start of next year, the restriction on participation in individual retirement accounts (IRAs) to persons who are not covered by employer-sponsored plans will be lifted altogether. Instead, any working person who can afford it will be able to put up to $2,000 annually into an IRA.

This money and the interest earned is deferred from taxation until the taxpayer reaches the age of 59 1/2, when it can be taken out. At that time the money and the interest are subject to taxation, but the deferral of taxation over the years while income is building makes IRAs advantageous from a tax point of view.

These advantages, particularly for persons in high brackets, make it worthwhile for a person who only wants to postpone taxation for over five years to put the money in an IRA and pay what amounts to a 10 percent penalty in the event of an early withdrawal, according to congressional analysts.

In a number of ways, the 1981 tax bill encourages both partners in a marriage to work. The IRA provisions mean that a couple in which both spouses are working could put $4,000 into an IRA annually, while couples in which only one spouse works can invest a maximum of $2,250.

In addition, starting next year, working married couples will be able to take a deduction of 5 percent, up to a maximum of $1,500, of the lesser-earning spouse's income. In 1983, this will grow to 10 percent with a $3,000 ceiling.

Further, the child-care credit has been increased from a maximum of $400 for one child and $800 for two or more, up to $720 for one child and $1,440 for two or more.

Along with these provisions, the tax bill retroactively altered the tax liabilities of persons who sell their homes. For persons over 55, the exemption on taxation of profits made from the sale of a principal residence was raised to $125,000 from $100,000. For anyone selling a house, taxation can be avoided if the profits are reinvested in another home within two years, instead of the current 18 months. These changes apply to sales closed after July 20, 1981.

In a very similar pattern, the maximum rate on capital gains was lowered, effective June 10, l981, from 28 percent to 20 percent.