The audio section is a better resource than here, but the basics invlove a shotgun mic such as a Sennheiser 416 in a zeppelin (Rycote makes some good entry level stuff as does k-tek)and booming it close (k-tek makes the best booms but gitzo carbon fiber ones are also good if a bit cheaper). The mic feed should go through a mixer such as a Sound Devices 302 and on to a digital recorder such as the Sound Devices 702 (if you get a recorder as nice as this, you can get away without a mixer, but it is not ideal as the faders are not great but it does have good pres, low cut and great meters).
You can also use hidden lav mics but good wireless is expensive ($600-2000+ per channel) and cheap wireless is junk. Basic entry level wireless is sennheiser 100 series and runs around $600 per channel plus mic ($2-400 for a good one). Boom is a much better option.