A good question.
The Simple Answer
Find your place of work on Google Maps and click Directions. Put in your starting point and it should start to navigate. Click the transit icon to see your transit options. It’s this thing.
You’ll see a list of ways to get there using transit. The first one is usually the best (for definitions of the word). Here’s what it will look like.
You can see that the recommended route to your great job at Zoo Atlanta is via the Red Line Train to the 21. If you click on it, you’ll see the details that show what train station where the 21 bus stops (It’s Five Points, by the way). You’ll also see what stop to get off the bus at to walk to the Zoo (Memorial & Cherokee).
The More Complicated Answer
Figuring out “the best way” can get really complicated. Keep it simple to start with and improve your route over time.
There are lots of buses in the network, and more than one will “get you there.” That may mean a 5 minute walk. It may mean the bus stops right out front of your office. It may mean that one bus is better in the morning but another better in the evening. You’ll just have to investigate and experiment to see what works best for you..
The Transit App works similarly to Google Maps and uses the same data to give your directions. It has the advantage of only working with transit, so you don’t have to tell it to only show transit in the directions.
The Details
You can see the routes on a map, but timing is more important. Pay attention to the times you are scheduled to arrive and depart your station or stop. Depending on the schedule they’re running, you may have to wait for a while to transfer from the train or between buses.
Just this weekend, my bus at Kensington Station was 45 minutes out when I got there, so I decided to just walk the 30 minutes to my destination. That was an easy decision (that I regretted the next day with sore legs) due to the timing, but you may choose to be seated on a different bus for a little longer than wait for a bus at an uncovered stop on a cold, rainy day with no place to sit.
If you have to walk for some period of time, check that there are proper sidewalks on the recommended path. Atlanta isn’t exactly the most pedestrian-friendly city in some spots, and you’re bound to run into some places that don’t like the use of feet to locomote.