Date: 201508
Local time of day: 1201-1800
Location: LGA.Airport, NY
Flight conditions: VMC
Light: Daylight
Aircraft: Large Transport
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground LGA
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction; Confusion; Communication Breakdown
Second reporter function: First Officer
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Detector: Person Flight Crew; Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Provided Assistance; Flight Crew Returned To Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Human Factors; Procedure
Primary problem: Procedure

Narrative: Holding on taxiway waiting for further instructions to taxi to runway. We were holding behind another carrier. There were at least 20 aircraft holding on three to four different taxiways waiting to takeoff. ATC told the other carrier to follow a second carrier to runway and then told us to follow the second carrier to runway. After the second carrier passed; the first carrier followed them and so did we. There were no other second carrier aircraft in sight. After about two minutes; Ground questioned us as to why we did not follow the second carrier (who was now on runway taking off). We said we did; he was now on runway.Ground stated there was another aircraft from second carrier. We looked around and could now see an aircraft from second carrier coming out of an alley way way down by terminal. There is no way we could have seen him from our previous position. ATC did not say follow the second aircraft.ATC needs to use proper phraseology and be clear as to which aircraft to follow. Ground Control was very busy and talking nonstop because of reroutes and congestion. When this is occurring it is very difficult to break in and question instructions. This is when ATC really needs to be clear with instructions. We don't know what we can't see and rely on ATC to be clear and concise.


Second narrative: During taxi to Runway 13 we were instructed to cross Runway 22 on Taxiway G and then turn left on Taxiway AA. We were then instructed to turn right on Taxiway E to BB and hold short of Taxiway G. During this taxi; Ground Control instructed us to contact Clearance for a full new clearance. Upon return from Clearance Delivery; we were instructed to follow Carrier B (which was taxiing on Taxiway G in front of us as we were behind a Carrier A aircraft; also holding short of Taxiway G. As the Carrier A began to taxi; we followed. Ground Control then asked us why we did not wait for Carrier B. We explained we did wait for the only Carrier B aircraft we saw. Apparently we were to follow another Carrier B aircraft that was just then crossing Runway 22 on Taxiway G. Ground Control's use of non-standard phraseology led to this confusion.


Synopsis: Pilot and Copilot reported an instance where there was confusion on who to follow. Pilots were told to follow second aircraft; which they thought they did. Controller wanted them to follow an aircraft they did not see. Pilots complained of controller's non-standard phraseology.