Reversing motor polarity ?

I just finished assembling a tracked base on which I hope to eventually mount my MCU. Each motor requires 3V and if my multimeter did not fool me draws 300mA max. Direction of rotation depends on the polarity and the bare bones base has a simple manual switch for flipping polarity. Now what's the best way to control motor operation and direction electronically from a 3V, max. 20mA output ? Use a relay (coil or solid state) ? Mosfets? If this was unidirectional I would probably add a mosfet as switch, but I don't know how it would deal with reverse polarity...