Do you block spammy-looking ads

Yes.

And, if so, what is your criteria for blocking them?

I block all those ads with a big green or blue "download" button. They look misleading, and they lead to downloadable toolbar for web browser, which are pure adware.
I also block all ads about "PDF" (which often are the same than the above).

do you only block ads that don't relate to your site's content?

No. I block only the ads above. Ads not related to the content of my sites, can be related to the interest of the visitors.

How often do you review your ads

Twice a day. At the same time I check my Adsense account. In the morning, and in the end of the afternoon. I am checking my account twice a day, to ensure there is no problem / warning messages, so I take the opportunity to review the ads.

I'll add that I do block each creative, and I also block the target URL "root".

Thanks so much for your answer! I was also thinking about blocking the very types of ads you mention.

May I ask what you mean by "block each creative" and "block the target URL root"? I'm afraid don't understand these terms. Thanks!

May I ask what you mean by "block each creative" and "block the target URL root"? I'm afraid don't understand these terms.

In the Ad review center, you can block individual creatives. Which is what I am doing. But I am also blocking the URL of the advertiser, so that other creative for the same site are not showing at my site automatically.

Pixby8,

My practice is I don't intentionally send someone else somewhere I wouldn't want to be.

That sometimes means avoiding things such as justpassing mentioned previously.

I won't intentionally send someone to a particular site even though it seems to be popular with other people. It's all about having a "reputation" you are proud of and then sticking to it. It benefits you in the long run.

FarmBoy

My practice is I don't intentionally send someone else somewhere I wouldn't want to be.

This makes me think, that I am only blocking Facebook ads :">

Why do you block Facebook ads? They seem to simply ask the user to check what's going on with their friends and don't seem spammy to me. Is this an ethical issue to you personally because they trade in users' data, etc? Just curious.

Why do you block Facebook ads?

So far as I can tell Facebook is botttom fishing, that is they are picking up left over inventory for pennies a click. They are then redirecting this traffic to the FB wall-garden (more like barbed-wired fenced garden) to have them click on high paying ads. They are engaging in "arbitrage" in a predatory manor. Not to mention the fact that they are skimming the users off with great search history, so that FB can immediately target users with ads based on interests gleaned from your site's content. Advertisers, then go to bid at FB because they get better click through rates and engagement, thus leaving your site with fewer relevant ads giving FB an even bigger opportunity to steal your users.

By blocking FB ads your are able to keep the users that you spent a lot of money and resources acquiring and thus increasing the probability that these users will click on the high paying ads.

This applies to other advertisers as well in varying degrees, such as click bait ads and green-button type ads. The spammy advertisers wont steal you "relevant" advertisers just your users but they still must be blocked.