That's a very general question. I'd need more info in order to answer it.
For example, in our manuals, we are required to set the ILS mins for an approach any time we use the ILS for guidance. So in other words, even if the weather is clear and a million, our altitude alerter has to be set for the IFR mins of the approach. On a nice weather day this number really doesn't tell you anything and it is much more useful to have 1000 AGL set as there is a standard "1000 foot" call and, in the event of a go around, we have our acceleration altitude already set. I would say about 80% of the crew routinely set 1000 feet and hence are violating SOP. There is a guy on this forum who does line checks at this specific company and he could probably better answer it, but I'd bet either a) people just follow SOP when getting checked, or if they forget they just smile and nod when they are reminded of the correct procedure.
However, more serious stuff... like going below mins with no runway in sight, that might get you pulled off line for a while, assuming you were caught.
And the getting caught aspect is a whole other issue. NORMALLY, when somebody does something wrong (intentionally) it goes to pro standards and they try to deal with it within the union infrastructure before the company gets involved. That way, they may be able to correct the problem and save the person's job. Unfortunately, they aren't able to solve the problem (or people go directly to the company first) and the person violating SOP gets some time off or let go.