Even with a 401(k), the IRA should be part of your savings right after the 401(k) match. In other words;
- Deposit to 401(k) up to the match
- Pay off high interest debt
- Deposit to IRA to max
- Back to 401(k) till maxed.
With 401(k), you'd need to decide Roth or pretax (Traditional), if the company offers both flavors. With IRA, the choice may be taken away if you have income over the limit.
Given Dilip's comment below - I'll clarify that the above should be planned in advance. Before the year, will you plan to save more than the matching percent? will it be more than $416.67 more per month? (The amount to fund the IRA). Etc. Not that you'll actually change percents as the year goes by, although I do suggest that for people who knock off their debt and wish to bump their savings after that.