You stand there, hovering between your recycling bin and your trash can, holding an empty two-liter pop bottle and a pizza box. What’s the right move? Are you saving the planet by tossing them both in the recycling bin? Or does this mix of greasy cardboard and sticky plastic belong in the trash?

The answer is: it depends.

With Earth Day approaching, we gathered facts and talked to experts to create a short guide to best recycling practices in Pittsburgh.

1. Learn the rules and numbers

To start, know the basic rules.

Throughout the city and in many suburbs, paper and cardboard can now be recycled with the glass, cans and plastic.

But, and it’s a big but:  all recyclables should be rinsed of any liquids or food waste. If they’re not clean, you’ll contaminate the batch.

Bottle caps can’t be recycled. So drop that rinsed two-liter pop bottle in recycling but put its cap in the trash.

Paper and cardboard should be recycled unless they’re too soiled. So that greasy pizza box we talked about above is trash.

If cardboard is clean enough to recycle but it’s corrugated, it should be flattened and bundled separately from the rest of the recycling.

For plastics, follow the numbers: Inside the universal recycling symbol (the triangle of arrows) on many plastics, you may see a number inside. Most numbers are recyclable. But number 7 (which can include BPA) may not recyclable, and 6 (including styrofoam cups and takeout containers) definitely isn’t. For more details, visit the city’s site here.

2. Make a plan for larger items

Due to the landfill ban imposed by the Department of Environmental Protection in 2013, the City of Pittsburgh does not collect big items like televisions, computers and other electronics. Instead, the city’s Public Works Electronic Waste Disposal page offers a list of electronics retail stores, centers, hauling companies and other services that provide proper disposal options. You can also check (see down below) on big item collection dates in your neighborhood.

3. Ditch the blue bags

Those blue bags you probably use to put out your recycling go directly to the landfill. They can get caught in machinery at sorting facilities, which can lead to downtime and safety issues for the employees tasked with removing them.  Use a bin instead; any color will do.

Why do we have blue bags in the first place? Justin Stockdale, a director for the Pennsylvania Resources Council (PRC), attributes them to Pittsburgh’s “Choose Your Own Adventure recycling system.”

“When you go back to the early ’90s when Pittsburgh implemented recycling, it was a state mandate,” he says. To participate, people found the least expensive way. This led to residents either buying blue bags or using the free grocery bags. As a result, the “blue bag” became a habit for many families.