Actually, if you mean that collector current (when the transistor is in saturation [i.e. fully 'on']), when you say 700ma, then, figure that the Vce is going to be around 0.1 volt, so the resistor on the collector to limit the current to 700ma, would be:
(12 - 0.1)V/700ma = 17 ohms
Now, if it is any more complicated than that, i.e. there is something else in series with that collector resistor, then you'll have to tell us about it.
What Boi is talking about is needed for determining the base resistor. And the Hfe (or beta) to use is the minimum possible Hfe for the temperature range of the application. To rely on the Hfe to limit the current at the collector is not a good idea, because the Hfe can vary tremendously from one transistor to another (even among those with the same part number). It also varies with temperature (and will vary as the transistor heats up).
Also, for the transistor to be fully on, the base resistor needs to allow a little more than the current required to allow 700ma to flow in the collector. This will insure that the transistor is in saturation, and not in it's active region. More current in the base will push the transistor further into saturation and reduce the Vce slightly. The drawback is that the transistor will switch more slowly. So, if speed is an issue, then you need to bias the transistor so it is right at the edge of saturation.
If that 700ma is to be drawn with the transistor in it's active region, then you need to consider the transistor's maximum power handling capability, too.
