Condensate water is often overlooked in both design and construction work, but is important to consider. Condensate water is normally produced as a byproduct of HVAC equipment. The most obvious would be at the evaporator, but that evaporator can be part of a packaged unit or separated out in a split HVAC unit. More importantly, these units can be in a number of locations which dictates the need for condensate lines:

Roof-top Units - Depending on local building codes and requirements, the condensate from roof-top units can be redirected to drain directly to the roof, or to be plumbed to either roof drains or even sanitary sewer lines. If plumbed condensate drain lines are required, make sure that detailed drawings are provided that spell out any air gap, p-trap and ventilation requirements.
Exterior pad-mounted units - Again, depending on local building codes, HVAC units that are mounted at the exterior of the building can drain their condensate to a landscaped area or a french drain or similar location. However, what is often overlooked is the path that this water takes. Whether it is plumbed with a drain line or drains directly from the HVAC unit, make sure that it doesn't cross any sidewalks or would possibly stain an otherwise clean hardscaped area.
Interior Units - Interior HVAC units are the most easily overlooked and potentially problematic in terms of condensate drains. Since condensate is by its nature a gravity-fed system, interior HVAC units that generate condensate water often need a condensate boost pump to reach a sewer or vent line to properly drain. Make sure each location where a condensate pump is needed is identified, that each pump is listed in an equipment schedule, that the electrical drawings allow for power for these pumps, that mounting details are provided, and that access panels are provided for maintenance and future replacement.