My MIL doesn't think the sun shines out of her son's arse. She doesn't make clear that she thinks he could do better. She has taken time to get to know me (so when we have dinner at hers there are no carrots on my plate because she knows I hate them - little things).
She'll give suggestions and opinions, but never makes any comment if we don't take them up (not even when an 'I told you so was quite warranted'). She and FIL very much believed they had their chance at parenting so they respected it was our turn, in fact the "you will get things wrong, you'll change the way you do it because you baby hasn't read the same manual as you. We all fucked up sometimes, but you get through it" from her was one of the best bits of advice I had. If she didn't agree, like she struggled with BLW because she was scared of choking, she researched it and either stayed quiet or actually said "btw I looked into that and I wish they'd had that when mine were wee" or something similar.
She also made it clear when we met that if she was too over the top or was annoying I was just to say. And she meant it. We once had a very frank, but polite and civil, chat about the fact my habit of tapping my foot constantly annoyed the shit out of her and she made me a deal that she'd stop whistling if I stopped tapping.
We're not rivals for DH's attention and she fully expects his loyalties to be with me and the kids first and foremost, rather than to her and FIL.
Basically she treats me like she'd like to be treated. Today she's done the school run so I don't have to take the little uns out in the snow. she didn't have too, but just offered.
I think the little things are the big things a lot of the time.