Hi Geoff,
"Best" depends on a lot of things: environment, other musicians and where they are in relation to you, the sound you're after etc.
You can just mic up and go straight into the PA mixer. Personally I like to have my own dedicated acoustic combo so I have control over my own anti-feedback facilities, tonal colouring and EQ and (to an extent) volume. So, I use an amp that has XLR inputs for mics.
The combo (a Marshall AS50 D) has balanced XLR and line outputs so I can take it through the PA for bigger venues that need more volume.
As for mics. A Shure SM57 or SM57A is a safe pair of hands (IMO the SM57A may be more suitable for a uke, but YMMV), as is the PG81 condenser from Shure's "Performance Gear" range. Actually, the PG81 is currently my preferred stage mic for instruments as I've had better luck controlling feedback with it.
You'll need to experiment with different gain/volume settings to get a balance between the mic picking up your uke loud and clear while still avoiding feedback and rejecting ambient noise.
If you opt to mic up instead of using a pickup then feedback is something you learn to live with and how to tame. It's an occupational hazard for the musician with a mic, but quite possible to overcome with a bit of preparation and care.
Feedback can be reduced or cured by the use of phase and /or notch filters, so look out for amps that offer those. Also, an EQ pedal can help beat feedback as you can cut the frequency range(s) where the problems are occurring. Boss and Behringer both do 7 band EQs.
Lastly, if feedback raises its head and all else fails, try moving yourself and your mic back further behind the PA and/or amp. Also, keep your hand resting across the strings while you're not playing.
