The goal is to combo Lock and Load with Spare Parts and other low-costing spells to gain card advantage, and burn cards to win.
Mulligan for cards like Elekks, Scientists and Animal Companions that you can throw onto the board in time. Generally you want to save your Lock and Load till turn 5 or 6 at least, to gain at least 3 cards out of it.
Against Combo Druid: 50-50. In fact I won all 4 matches against them, but I feel that I was being lucky. Just try your best to play on curve, and you can do tricks like Deadly Shot a Druid of the Claw to gain tempo advantage.
Against Control Warriors: 60-40. I feel that this match is slightly favored since CW's threats come slowly, so you can get much value from Lock and Load. Bait out the Brawl and then swarm the opponent. There's even a chance that you can win the fatigue game, if you can get big drops from yourLock and Load.
Against Secret Paladin: 25-75. If you don't fall behind from the start, you stand a chance. But you still can't survive the Mighty 678. If you tech in a Pyromancer, the matchup can be helped.