I don't have the competition experience of others (yet!).
As put above, it depends on your context, goals, and dog's current behaviors.
Targets can work well (to prevent an incorrect retrieve which would be reinforcing to the dog). But recently I've just been starting with dog in front of me sitting (not in a formal "Front" position). Cue the dog to wait. Toss an object straight out to your right. one off to the left. Cue a retrieve to one and then the other. Vary which one you send the dog to. After a number of reps, repeat with the dog in Heel. Each session work towards the objects being closer together or adding in another. In 2-3 sesisons we were throwing out 4 items and had over 90% correct responses. The errors did not involve wrong item retrieval but rolling on the item....something I need to work on!