Actions and Timing
Most things a character tries don't require a roll. Walking into a tavern, drawing a sword, having a conversation - if there's no meaningful obstacle or uncertainty, just describe what happens and enjoy it. The dice only come out when the outcome matters and success isn't guaranteed.
When you do need a roll, it will be one of these.
Free Actions
Some rolls don't use up your turn - they happen in response to something else or alongside your main action. Common examples include resistance rolls when someone tries to affect you, quick perception checks to notice something happening around you, or memory rolls to recall relevant information mid-conversation. Opposition rolls for free actions are implicitly also free so long as you have a reasonable justification...
Direct Actions
Tackle a problem head-on. Punch the guard, climb the wall, haggle a lower price. Each success chips at whatever stands in your way, making the obstacle weaker and your next attempt easier. When you accumulate enough progress you've overcome the challenge entirely.
Direct Opposition
Opposition rolls are really just a compression of the usual sequence. Rather than you acting and them resisting, then them acting and you resisting, instead both sides roll simultaneously and compare results. This keeps the action flowing and reduces "swinginess" while representing the give-and-take of real conflict, but you can always do it the long way if you want.
Note that actions can be simultaneous, which is what opposition shows. Even if you do each piece separately, they can be happening at the same time; that's one way both combatants can kill each other. Another is bleed damage, or poison… Be as detailed and realistic as you need.
Boost Actions
Sometimes the smart move is to take a minute and set yourself up for success first, rather than charging ahead. Create the advantage you need - study your opponent's fighting style, offer the client a drink to soften him up, maybe drink a potion first, or set up incense and sigils before a summoning. Success gives you a temporary bonus that makes a following action more likely to succeed.
Opposition to a Boost works the same way. If you think someone is studying your fighting style, you can always try to disguise it. The client might turn the tables by accusing you of trying to get him drunk.
Boosts With Duration
For boosts that should last longer than the next action, use the Wagering mechanic to dedicate persistent points - generally such fabricated Boosts last the rest of the scene, though the GM may rule that it goes away sooner, or lasts longer, as appropriate.
Free Action Access to Pre-existing Boosts
Sometimes there's already something available in the scene that would help an action, just sitting there waiting to be added to a roll. Players can always propose an idea, and if the GM agrees he can declare the roll to use/incorporate that Boost as a free action. If you see that the knight has backed himself up to the fallen log, it's reasonable to body slam him back in the hope that he'll trip over it - the log is an environmental factor the player can roll as a free action, because it takes no time to set up. The value of the roll is added to the attack EL, and can be included in splits or Wagered effects.