At Bubble Witch Saga level 34 I have found out that there can be really various mixes of bubbles sets, both in the starting cauldron and on the board to be cleared. That means that sometimes you get many bubbles left when breaking the ceiling, other times even +7 isn’t enough! :/
I think that clearing the right side first helps a lot. It gives you the opportunity to clear out Bubbles to the left, that you otherwise couldn’t reach. After you have cleared out the right row you just use your angle shot skills and can easily access those Bubbles that are unreachable if you don’t shot via the right wall!
Another good reason to clear out the right side first is the problem area under the right upper black bubble line. That tends to be unpopped and you really need to pop every bubble under the purple line in the strategy picture to reach the ceiling.
3 Star isn’t really that hard, if you play with the available Charms at Level 34. (Value ~40 US Dollar, click THIS to read more about the charms) // editor’s note: the charms are no longer available.