Most beginning options traders try to leg into a spread by buying the option first and selling the second option at a later date. They're trying to lower the cost by a few pennies and it simply isn't worth the risk.
Don't leg in if you want to trade a spread. For example, you might buy a call and then try to time the sale of another call, hoping to squeeze a little higher price out of the second leg. This is a losing strategy if the market takes a downturn, because you won't be able to pull off your spread. Now you're stuck with a long call and no strategy to act upon.
Sound familiar? Most experienced options traders have been burned by this scenario, too, and learned the hard way. Trade a spread as a single trade. Don't take on extra market risk needlessly.
How can you trade more informed?
If you are going to try this strategy, you don't want to buy a spread and wait around, hoping that the market will move in your favor. You might think that you'll be able to sell it later, at a higher price, but that's an unrealistic outcome.
Instead, use Ally Invest's powerful trading tools to trade the spread at once. Don't try to deal with the minutia of timing. You want to get into the trade before the market starts going down.
Always, always treat a spread as a single trade!