How can I tell what level raid I'm looking at

Two ways to check.

1. Check under the Raids tab. Tap the bottom right button that takes you to Sightings, then swipe right.

2. Tap on the gym itself, then tap the bottom left button with an egg symbol.

By the way, do not try to solo anything that is tier 3 and above.

Also: The raid egg indicates the level. Pink egg is level 1-2, yellow egg is level 3-4 and blue/black egg is level 5. So you can easily identify doable raids by the pink egg.

All level 1 raids should be easy with whatever the game autoselects for your fighting team, but for some level 2 bosses you may have to look up what counters you have. Flareon or another strong fire-type should be good for all level 2 bosses except Alolan Exeggutor. For the Exeggutor, ice-types would be the best.

When you click on a gym with the egg over the top, you will see the defenders and a little egg in the lower left corner of the gym graphic. When you click on the egg in the lower left, it will enlarge the egg and show it with skulls over the top of the egg. The number of skulls equals the raid level.

If the egg has already hatched and you click on the gym, there will be a number of skulls over the boss. The number of skulls equals the raid level.

As level 15, choose pink eggs only for solo. In fact you may only be able to do Level 1 raids reliably.