I has bought these tickets 2 weeks in advance online and I picked them up about a day before departure. The total came to about 17 dollars Canadian (which is pretty cheap in my opinion considering it's a ticket for Vancouver to Seattle).
After we went through pacific central (who's architectural looks pretty vintage), we boarded our bus. I encountered a lady from china who didn't speak mandarin (but I did... Well only bits of it), so I was able to help her fill out her papers and talk to the bus driver when we boarded the bus. The bus itself was a bit old, you can tell that through the fact that some of the chairs were all dirty, some levers that lowered the chairs were missing their handles. Never-the-less, you get what you paid for right?
Once we left Vancouver the bus did a quick stop at coquitlam, before heading to pacific crossing for border inspection. In my opinion, this part of from coquitlam to the border felt long compared to the latter half of our journey.
After we cleared the border, we made a pit stop at Bellingham, Mt. Vernon, and Everett before arriving at Seattle. We got a few minutes to walk around in Bellingham and I noticed that the locations of these greyhound stations are somewhat far from the city center (so if you haven't taken a greyhound before and would like to take one, make sure you plan ahead so you know how to get to your destination). Another thing I learned is that once you disembark the bus to go explore, there may be other passengers who is boarding the bus too, we had our seats taken once, so ik recommend if you would like to explore, bring your valuables with you, but leave a bag or something on your seat so that others know it's occupied.
Once we arrived in Seattle, I realized how convenient the greyhound station for Seattle is located. The building itself was abit old, but still functional. When we exited the building, I noticed that it was very close to the hotel we were staying at. In a few minutes of walk from the station, there were numerous Starbucks and fast food places.