We always play scenarios.
- take and hold (strategic points) - forces you to gain ground as soon as possible
- defend the line (forces only one army to attack)
- retrieve the arifact (this forces to play really fast and to use units that usually avoid combat - rest of the army is for support)
- turn limit is also welcome
- limited visibility + shorter distance of deployment zones
Everything mentioned above will do any good if:
Familiarity with the rules allows for quicker gameplay. Agreement between players to not look at the rule book every time that there is a minor technicality.
Arguments considering rules eat most of the time.