The House Ways and Means Committee will meet Wednesday for its first session to redraft the tax code, beginning with the crucial question of how to proceed in writing the bill.

Although the meeting is not expected to deal with the substance of the tax changes, the decisions made Wednesday and possibly in later sessions will play a key role in determining what kind of legislation -- if any -- the committee ultimately produces.

"The rules are going to be the most significant of votes to begin with," said Rep. Raymond J. McGrath (R-N.Y.). "They will either expand or narrow the parameters of being able to make changes in the bill."

Writing the rules also will be something of a preview of how Ways and Means will handle tax revision. Chairman Dan Rostenkowski (D-Ill.) must deal with the 35 fragile egos of members who, if they feel left out in shaping the committee bill, will be more likely to balk at the final product.

And the procedural debate will be the first test of whether Rostenkowski can persuade the committee to go along with decisions he has made.

"He wants the members to feel they're part of it," said Rep. Barbara B. Kennelly (D-Conn.). "It's down to the 36 of us now."

Rostenkowski is still deliberating on the bill-writing process. "He's got a notion" about how to proceed, but has not made final decisions, committee spokesman John L. Sherman said.

As they debate tax revision in closed session, beginning Sept. 26, members will have a draft of several alternatives, including the current tax code, the Reagan plan and what aides are calling "staff options."

Those options, which will cover most of the controversial provisions, will not necessarily have Rostenkowski's endorsement, but will represent "the best intersection between politics and revenue," Sherman said.

Here are the procedural issues facing the committee at Wednesday's meeting:

*Money. Without a requirement that amendments to retain deductions be accompanied by proposals to offset the loss of revenue, the tax plan would quickly be picked apart. Tax writers will have to decide whether every proposal must be "revenue-neutral" -- neither increasing nor decreasing the amount of tax revenue collected -- or whether they will only hold broader sections of the bill to that standard.

*Timing. Should the cut in rates be enacted first, to give members an incentive not to preserve deductions? Or last, so that legislators will be able to tailor the level of rates to the extent to which they have broadened the tax base?

*Discipline. Rostenkowski will have to decide whether members with amendments will be allowed to reopen sections of the bill that have been decided. That seemingly obscure issue may be one of the most important factors in determining whether the committee bogs down for weeks or whether it can stick to Rostenkowski's optimistic timetable and complete a tax-overhaul bill by mid- to late October.

"We have to be able to reconsider things," said Rep. Sam M. Gibbons (D-Fla.). "But we have to draw a reasonable line or someone will just dilatory it to death."