aww

I'm always a big fan of a strong backlight on furry animals like this. try to catch them at golden hour with the sun mostly behind them. you'll either need a bit of fill light or to bring the shadows up a touch in post for it to really pop in that situation. if the dog is patient you can literally just use a piece of foamcore board to bounce the sunset back into their face. in this photo i even had the sun flairing into the lens a little. it helped that i was shooting up a hill. made it easier to line up the sun, but i was still laying on the ground to get this.

as I mentioned in the post you'll want to open that aperture to get a nice dreamy shallow look like this. you also want to get as close to the subject as you can while maintaining a good frame (fill the frame) and make sure the background is far away. an open field works great for something like this. you should also always try to be at your subject's eye level as a general rule of thumb. yes, being higher or lower can work, but there needs to be intent behind doing it.

shooting very large dogs like that will make it much harder to get a photo like this one. the 45 1.8 will seperate the subject well, but it won't blow it out into a dreamy blur like this when aimed at moose dogs. you'd need something longer like a 135 1.8 or an 85 1.2. that said, you can still make a very nice looking portrait, it just won't quite look like this.

you also don't want it to be overly sharp. sharpness tends to make the fur look less soft and cute. if it's like a doberman doing a nobleman pose then you probably want a sharp look, but if it's a cute little puppy like this one i tend to remove sharpness in post or shoot on vintage glass.

it's not cheating to use treats to pose them. it's not unreasonable to take a nice picture of the owner holding them. if all else fails, just chase them around at their eye level on burst mode. try to catch the sun lighting then up nicely from behind.