If you have a minion that does something beneficial to/for another friendly minion (e.g., Crackling Razormaw or Argent Protector or Plague Scientist), and you have nothing else to do that turn but perhaps use your hero power (say maybe you're out of other cards in your hand and have no minions on the field), what do you do? Do you play that minion and throw away its battlecry? How long do you wait before sucking it up and playing that conditional battlecry minion? (say if you keep drawing spells).
This is the basis behind the 'value' and 'tempo' choices that make up the majority of choices in HS games. The 'value' option would be making the most of your cards, such as making sure those battlecries find targets, while the tempo choice prefers focusing on fighting for the board and using your mana efficiently. This also comes into play when it comes to removal tools: Do you use defile to remove that 1/1 or hold it to try to kill more minions.
The answer: it depends on the situation. The overall question you have to ask is: how am I winning this game?
For example, if you are up against a murloc deck, murloc decks typically lose by losing the board as they want to win by snowballing with buffs between each other. Thus you'll want to focus on winning the tempo game sometimes sacrificing value to do so. If that razormaw played alone means you can knock out a murloc board next turn then you probably will win more than way than holding it and trying to drop two minions while your opponent has 3 murlocs and a warleader slamming your face.
OTOH, if you are against a control deck like, say, a shaman, chances are you aren't going to be able to roll that razormaw into an offensive threat. Thus you are probably better off trying to create a strong board slightly later on that may be able to get past their removal.
THat is, unless the murloc deck is a paladin midrange deck without an early murloc push, thus making you think that it has a strong late game you might need to counter with a strong board and that 3/2 won't cut it. Or else that shaman seems to be more control based and, thus, will be able to easily take down your bigger threats so your only hope might be going aggressive early on with tempo pushes.
So, yes, the answer is NOT easy. This is actually the point where you get past "oh the game is easy, just play the best card." and get into why pro players play thousands of games and stop to think about their turns so that they know instinctively when to play that card early and when to wait.
OMG final note!!!!
There's also a possible question of your deck as well. If youare finding yourself regularly in a situation where you can't regularly get value from those cards, it might be the case that your deck isn't giving you the setup to get that value. For example, if you typically don't have that early game card for your razormaw then you might need to:
1. Add more 1-2 drops so that you not only have more cards to have for razormaw setups but also possible alternatives so you have a play that lets you drop something on the board while holding back the razormaw.
2. consider dropping that battlecry minion and opting instead for a card that gives you more tempo. This is actually why many rogues don't play Plague as they tend to play decks that can't reliably use that battlecry properly.
So that's also a consideration. A good card in a deck that can't use it is a bad card.
One does not simply walk into Mordor,
unless they want to be the best they can be.