After several years of always-near-100%, everything-is-a-competition conditioning, his ideas on the subject are rather refreshing. You don’t always have to go full bore, in fact that is actually detrimental to progress. He wasn’t the one who came up with that idea, obviously. I just like how he puts it -
Our goal is to do the least amount of work necessary to get the adaptation we’re after. (paraphrased from one of his videos)
If you aren’t sure where to start, dig through his older articles till you find his 4-week conditioning plan. It introduces you to several of his training methodologies (tempo intervals, high resistance intervals, threshold training, etc) in one short go, and you can easily adapt it to a longer period of time.