I'd suggest a minimum of 30 year term. If you don't have kids yet, 20 year term is unlikely to cover you until your future children are out of college (no longer dependent on you).
And buy as much as you need NOW. It is much cheaper than if you wait until you are older (and possibly have health issues), and if you want more insurance later on, you have to buy a new policy (at then-current rates). In other words, you are not stuck with that coverage amount, but must apply for a new policy in order to increase your coverage.
As a side note, we've been very happy with Northwestern Mutual for DH, who is a cancer survivor (skip Nationwide - they were a pain). I have First Colony, the best rate we found for a healthy 32 year old female nonsmoker.