I'm not one to give advice as I'm only just starting on this journey (DS is 7m) but this fits last night's "Little Angels" perfectly so since no-one else has mentioned it I'll try to remember a summary.
Scenario was a single mum of 3yo triplets, two boys & a girl. Boys rowdiest but girl also joining in. Complete chaos, all exhausted, basically confined to the house, too scared to take them out alone.
After structuring mealtimes (setting positive expectations & giving praise rather than only negative commentary) and bedtime (calm bath/book etc and repeated placing back in bed; closing door for 1min if get out of bed) they worked on controlling the chaos.
Key thing (as in all Little Angels programmes as far as I can see) was time-outs. This one used 3 steps - having more than one child to keep an eye on clearly makes it harder. First stand in the corner. If child wouldn't stay in the corner, sit on the stair. They used a timer "sit here until this timer goes off" so mum could be back with the other kids. If still wouldn't stay put, shut in a safe room for 1min per year of age. That's the really hard bit and you have to stay holding the door handle and suffering the crying. Seems to work though, at least on these programmes.
The other main thing they showed was when out and about and the kids ran riot & wouldn't come back. After a running around game with a knotted rope to hold onto (showing that fun can be had near mum) She used wrist reins to keep them near, then let them free but kept occupied (at the zoo, lots of commentary) and then waved flag to get them to come back (avoids endless shouting). Sticker rewards for coming back.
I hope some of that is helpful to someone. I wish you all luck and cross my fingers for myself in a few years time :-)
Ducking for cover now... no idea what Mumsnetters think of these programmes. Too rosy maybe??