Are there any useful tips for playing soloq?
Have a large amount of characters you are good with to fill various roles.
I recommend at least:
1 hitscan DPS (McCree, 76, Maybe Widow)
1 flanker (Tracer, Genji, Sombra)
1 specialist (Mei, Junkrat, Torb, Sym)
1 anchor tank (Rein or Orisa)
1 bully tank (D.Va or Wintston)
1 off tank (Zarya or Roadhog)
2 healers (Mery, Lucio, Zen, and/or Ana)
Don't pick first, but don't pick last.
Use your voice to call out important things only. Call outs for "Mercy is 1" or "3 people on the payload please" are all you need. Using your Mic for anything else at all is risky.
If you are not comfortable with your team comp, say it in a non-passive aggressive way.
Saying things like, "We could really use a Mercy." does nothing. It makes people feel spiteful and antagonistic towards you. Instead try, "I'd feel more comfortable with a/another healer if you guys don't mind." If no body switch, then try to make it work, because you're much more likely to win with a group of people playing what they want, than 2 or 3 people bitching at each other for bad team comp for 15 minutes straight.