If coffee (or tea) is part of your daily routine, skip the paper cup and sleeve and bring your own.
Here's a few tips on features I find useful in a travel mug:
A leak-proof, no-spill top. Look for a lid that fits secure and has a snap-top closure (ie. something that covers the little drinking hole.) This feature will allow you to carry around a full cup without sloshing it about, plus the remnants that remain at the bottom won't spill out in your bag or the backseat of your car when you're finished.
If you're unsure whether the cup you're looking at passes, try the water test (either in the store if they're cool with it, or check the return policy to make sure you can bring it back if it doesn't.) Fill the mug with water, snap the lid securely in place, turn upside down and shake it around a bit. If it doesn't leak or spill you're in business.
Stainless steel. There are a lot of plastic travel mug options out there (first check to make sure it PVC free if going that route). Plastic is lightweight, which makes them easy to carry around, but can crack easily when dropped. Plastic also doesn't keep the beverage warm for very long.
Ceramic is another option (especially if it is lined with stainless steel). It is sturdy and durable, but might be better for around the office since ceramic mugs with lids don't often come in shapes that are cup-holder friendly.
I prefer stainless steel because it it durable, keeps hot beverages warm for the better part of a day, and keeps cold beverages cold. But like aluminum foil – keep it out of the microwave.
Know how many ounces your mug holds. I have a 16oz mug (equivalent to a Starbucks Grande hot cup) but would often be over charged at different places depending on how big the cashier thought my cup was. Most places serve coffee in 8oz, 12oz, or 16oz sizes. If you're unsure, or if your coffee place is unsure, do another water test. Fill up a paper cup with water. Pour into your mug. If it fills it up, that's the size you should ask for.
Also ask your coffee place if they offer a cup discount. By bringing your own, you're actually saving businesses money since you're not using their stock of paper cups. Many places will offer a ten-cent discount (others may not, but it doesn't hurt to ask.) Oh, and bringing your own mug will also make you more memorable to your barista/coffee server.
Amy says: I love my $20 blue, stainless steel, travel mug I bought from Starbucks nearly three years ago. With all the coffee I drink I've saved a lot of paper cups from going to the landfill. However, I'm also known to leave the house without my travel mug more than I should (mainly because I forget to wash it.) After cleaning it out at night I'll throw it in my bag so it is ready to go the next morning. You might want to consider keeping your mug at the office, in the car, or put it next to your keys or cell phone as a helpful reminder.
More Bring Your Own Tips from Rebecca: