1) Avoid account fees.

T Rowe Price charges $10/year for IRAs under 5k. Each mutual fund is a different "account", so if a person owns 6 fund under 5k, they will be charged $60.

If you ASK, T Rowe will tell you that the $10 fee is waived if you have 10k total in all IRAs.

2) Avoid frequent transactions. If using brokerages (to buy stocks, ETFs or mutual funds from other companies), there is a transaction charge each time you buy or sell. Solution- accumulate money in a savings account all year, then have only 1 purchase transaction per year.

If you get clever, you could save money over 2 years time, and in any of the first 4 months (before April 15), you could buy 8k worth of investment for same transaction cost... making sure 4k gets allocated to prior year and 4k get allocated to current year.

3) Avoid transaction fees on mutual funds. Sme funds charge a "short term" redemption fee. If you rebalance, and need to sell a fund (in a 401k or IRA), make sure you have held the fund long enough to avoid these charges.

If buying mutual funds through a broker, there are frequently 12b-1 fees, sales loads or other charges. This is money out of your pocket. Find no load mutual funds (all T Rowe Price funds are no load).

4) Avoid buying expensive investment products such as variable annuities. If you need an annuity, it is best to invest outside the annuity (in a mutual fund), then sell the mutual fund and buy an immediate annuity. The immediate annuity will have charges, but it's a one time thing when you create the annuity contract, not ongoing fees during the investment phase which drags returns.