-Do not take heal. Or TP or cleanse. Or anything other than exhaust or ignite.
For some reason, not a fan of taking ignite on a support. Exhaust, well I typically run exhaust. It would be nice to see more diversity in summs, but that would require rebalancing and new summs.
-Do not roam if you don't know how to roam. Don't leave your adc in a bad 1v2 where he's forced to give up turret or die
Well. Pretty sure that is obvious. On the counter point, an adc needs to know when to back off if they don't have coverage in the form of support/jungle. Farming under tower vs most non-displacement supports should be relatively safe.
-Do not build some troll shit, I understand AP is good on Sona but generally you want a sightstone tier 2 boots and an aegis pretty much every game.
Sightstone is pretty much the only thing I will ever require myself to build. Typically 2nd item. (Since I play mostly morgana, spell thiefs => Frostfang + pink (and maybe ruby), next back sightstone and boots if possible.
If I am going Sona, I am going Sona because I noticed my team LACKED ap damage. That is one of the reasons you take Sona. So a 2nd/3rd buy lichbane is beneficial. Picking supports is about team cohesion just as much as any other role.
-Do not sit back behind the adc doing absolutely nothing. Your job is actually to fight in lane, at least as much as it is the ADC's job. Don't be that sona that just stands behind turret all day.
That depends on play style. You could easily be taking a sustain support, or a disruption support instead of a poke or damage support. Sure, if I am leona I will want to be jumping into as many advantageous fights as possible. If I am nami, janna, soraka I might want to be healing and letting my adc out farm the enemy, because we might be at an early disadvantage.
-Do not take CS if you can help it. You have items and masteries that generate you the gold you need. Your teammates don't, that's why they are taking the minions. This goes for the entire game, not just laning phase. Obv I'm not counting relic procs.
If I am defending tower first blood, I'm taking CS. if I am shoving the minion wave into their tower because everyone has backed aside from me, and I will back as soon as I'm done, I'm taking CS. Basically, you aren't in lane? I'm taking it. If you are coming into lane and I can tell you will get there before it shoves into our tower? I will kill the ones that would have died without you there. I may even tank the wave to save it from the tower for you. I get there first in the later game? I'm taking it. I understand the flow of minion waves, and what happens if they get shoved in certain directions. I might not always be the best at turning the wave how I want it, but there is intent there.
I think there is 1 mastery that generates 3 gold every time you hit an enemy champion every 8 seconds. Another that generates 1 gold each time a minion dies around you that you didn't last hit. gold/5 runes seems to be in a terrible place. The gold generated is no where near enough for a support to deny themselves CS if they can get it. Sure, I'm not going to take it from you, and I'm not going to set the lane fully pushed if I can help it, but I will take CS if you aren't there.
-Do not kill yourself to clear wards or put me in a bad 1v2 position to clear wards.
One I know I need to work on in lane.
-In general stop acting like leaving the ADC 1v2 is no big deal, as I've seen a lot of threads claim it's ok to do this or even to leave lane entirely if you don't like how he's playing. This is basically turning your game into a 4v5 sacrificing your ADC's power like that. Everyone understands that when a jungler ganks mid you usually cant farm and fight while 1v2, so I dunno why you think it's different bot lane.
The difference is intent. The enemy adc will be wanting to CS mostly, the enemy support may be looking for an opportunity to turn the lane in their favor, but they are looking for an opportunity. A jungler gank is usually because the lane already has that opportunity there. Shoved up, summoners down, no ward coverage, open, low mana, etc. If our play styles aren't matching (say you want to just farm for late game, and I am playing a lock-down style support) i may roam for opportunities because I am more orientated to early game. Especially if the enemy is counterjungling, or mid is looking ripe.
If I deem the lane safely ahead, in that you have enough lead to where I don't think you can throw it, I might go support another lane that isn't doing as well. Because if you have a lead, I have a lead as well.