Here is some relevant information from the FAA:
TCAS Operations While on the Airport Surface - InFO 11012
Additionally it is a good operating practice to turn TCAS on in the TA-ONLY or TA/RA mode for a short period of time before crossing an active runway to double-check for the presence of any aircraft on short final. NOTE: It takes several seconds to display traffic when switching to TA-Only or TA/RA. The time period varies between different TCAS II equipment manufacturers.
http://www.faa.gov/other_visit/aviat.../InFO11012.pdf
Transponder Use by Aircraft On Airport Movement Areas - SAFO 15006
Operators should ensure that their procedures and manuals clearly state that flightcrews and general aviation (GA) pilots enable transponders to the altitude reporting mode and enable ADS-B Out transmissions (if equipped) any time their aircraft is positioned on any portion of an airport movement area. This includes all defined taxiways and runways on all airports.
http://www.faa.gov/other_visit/aviat.../safo15006.pdf
FAA AIM 4-1-20 Transponder Operation
3. Civil and military transponders should be
turned to the “on” or normal altitude reporting
position prior to moving on the airport surface to
ensure the aircraft is visible to ATC surveillance
systems.
NB: Selecting 1200 (equivalent to 2000) prior to shutdown or else is not mentioned. Separately, on many [new] transponders mode S there is no need to switch it to ALT, or any other mode, as it is done automatically.