[RPG] What are the likely effects of a wild magic surge

The table has a few very specific verbiages and they indicate how the effect happens:

• Controlled by the DM. This is what it means, a monster controlled by the DM appears
• You cast X centered on yourself. This means you cast a spell with the center point of the area of effect being yourself.
• You cast X spell. This means you cast the spell being in full control of the targeting.
• You cast X on yourself. The spell affects you, and you only.
• You cast X on a random creature. A random creature is chosen from the valid targets.
• As far as the size change, it says "for the next minute". With the height change one, you're just as likely to shrink, and you'd have to grow (or shrink) several times (like 10ish?) without a corresponding shrink roll to actually change size categories.

Wild magic is supposed to be unpredictable, that means sometimes you get to control the targetting, sometimes you don't Specifically with Magic Missile and the result where up to 3 creatures get lightning damage, the sorcerer is in control.

It does seem kind of intentionally-vague. I suppose that's so the DM and players can determine how much wackiness they want to inject into the campaign. Perhaps there will be more guidance for this in the DMG, when it comes out.

Like most things that are left up to DM discretion, this is something that the DM and players should discuss ahead of time, preferably before anybody rolls up a wild magic sorcerer. It's important that the player knows what the rules are, even if they're totally arbitrary.

Some options that would make sense to me:

1. Roll after every spell cast
2. Roll for a surge only when the sorcerer is under stress somehow
3. Roll for a surge only when it's potentially important to the story

Rolling for surges after every spell cast seems a bit extreme to me, given the chance of a TPK for some of those results, especially for a group of low-level characters. On the other hand, the really nasty results are a small chance, on top of the small chance of surging in the first place, so unless you had two unlucky rolls in a row...

I like the second and third versions, especially if you can work them into the character's background and personality. Maybe they're more-likely to surge when someone they care about is being threatened, or when their hit points are low, or whenever they're affected by a condition.