use whatever you can, dumbells, barbells, sandbags, bodyweight, sleds, whatever in your training to put together workouts for yourself and do them hard and fast.
i know thats a general answer, but you asked a general question.
if youre new to training, id suggest checking out
www.crossfit.com and doing their workouts maybe for 2-4 weeks. after this, you will know exactly what hard conditioning is supposed to feel like and youll have a better idea of methods you can use to condition yourself effectively.
hope i helped