1) Unless your blog's sole purpose is posting announcements, give some idea of what you liked about the work. But "Oh the pictures are so beautiful!" isn't good enough. What did you like: something about the technique? the theme? the emotional content? or what? And of course not all good art is beautiful. If you're ambitious, write a full-scale commentary. By the way, you aren't required to like everything: if something doesn't work for you, go ahead and say so -- but again, give some reasons.
2) If you interview an artist or curator, you should fix any mistakes in typing, grammar, and idioms. This is especially important when the artist is using a second language. (If you're both working in a second language, e.g. English, find a friend who can help). You're not going to somehow distort what the artist said -- on the contrary, you'll help them be understood clearly, without the impediment of fixable errors. Quotes from notecards are more complicated, but if you're writing before the official opening, work with the artist to make the corrections.
3) Check your SLURLs. Test the actual link you create. Having incorrect SLURLs makes it difficult or even impossible to find the art. I remember one time someone's SLURL landed visitors in the ocean, but the exhibit was up 2000 meters. Sometimes SLURLs are so malformed they don't work at all.
1) Don't gush. Writing about something is enough to tell me that in your view, it's interesting enough to merit an announcement. But fawning makes me roll my eyes. I'd rather read a post that simply tells me the work exists.
2) Photos: forget the selfies. Once in a while you may need a photo with you in it so you can indicate scale (in which case you're probably small), or to show outfits/avs that the artist offers. Otherwise, stay out of it. To be honest, I also don't see much point in photos of the artist. The exceptions are interviews and, occasionally, artists with unusual avatars.
There you go. Exciting.