Game masters, it will happen. Have no doubt. A player will come up with a brilliant, off-the-wall, and/or carefully-considered maneuver that gets them -and you- excited about the fight or obstacle at hand. They chuck the dice and BAM! it’s a... one.
Sometimes you can see the joy fall out of the player’s face and puddle into disappointment about his/her toes. That's when it’s time to remind 'em, the games not over yet.
For one thing, in my system at least, a one isn't an automatic failure. And even if a low roll and bonuses for aptitude/ingenuity/surprise/etc. can’t quite cut it, don’t let that failure be the end. With a well-chosen tactic even a miss should have some benefit. For instance, a player took advantage of your description of his character’s enemy. Riven, his PC, lunged with a dagger at an unguarded, lightly armored flank. The player rolls a 1 and misses. You could declare that “Riven missess his mark” and move on to the enemy’s attack, completely dismissing the tactics of your player. A better option is to acknowledge the miss, but reward the player and PCs quick thinking.
“Riven lunges inside, stepping right, the guard barely manages to roll her open left hip away from your blade. Riven’s made it inside the reach of the guard’s short sword; she’ll have to step back or try to grapple you. Either way the advantage is yours.”
For some players, who don’t see the immediate possibilities in these situations, you may have to guide them. Let’s say that a PC had just attempted leaping tackle at a slobbering orc and failed; she’s now on her hands and knees with the orc a couple feet behind her. Her player’s first instinct may be to declare that she scrambles to her feet. You might mention that she could also try to roll forward to put more distance between her and the orc; She might try to mule-kick him (bonus for surprise, but a miss puts her in a worse situation); or she may want to hold for a moment and then roll sideways hoping to sweep his legs with her own. By helping to coax the players along into more exciting responses and actions, you help to mitigate the disappointment of a poor role and replace it with bracing suspense and a deeper engagement.
I’m reminded of an actual fight I was in several years ago that involved the proverbial rolling of a few ones. First of all, I want everyone to learn from my mistake, don’t talk shit back to somebody until you’re done urinating. It was a busy Friday night at my favorite bar and a fellow I’d previously had an altercation with came into the bathroom whilst I was micturating. I’d had a couple pitchers of beer to myself already so this was set to be a good long pee. Anyway, he started talking mad shit to me and eventually called me a faggot. In response, I declared that he must’ve been looking for either a fistfight or a blowjob and I didn't think he was attractive. Well he picked fistfight right quick, and I ducked and covered ‘til I was done peeing. The fight ensued for a bit and I rolled a one on my coordination/dexterity/what-have-you check and slipped to my knees in a puddle of urine – not an enviable position. It did, however, present me with a unique opportunity. The redneck’s balls were now shoulder level so I drew back for a stronger, from-the-shoulder shot to his nads. Mid-punch, he rolled a one and slipped so my strike took him in the inner thigh. Between the momentum of his fall and my fist, he got knocked out of the bathroom and the rest of the bar got to jump in on the brawl.
The overall, real lesson to consider is that you should never let the dice completely override well-chosen actions. There certainly should be consequences for failed actions (without risk there’s no verisimilitude and it’s not really a game), but poor rolls don’t have bring everyone down. There’s winning, even in failure. Just look at Charlie Sheen.