Good topic and one I can relate to. In my opinion…
In terms of culture I would try to ensure there is alignment with the relationship of the key stakeholders of the deal. Meaning that pre-deal relationships should be strong and/or strengthened. Opinions on fairness, vision and ambitions should be similar and both parties should see a mutual benefit of being in a relationship with one another.
This is similar to operational alignment – both parties need to benefit i.e. the smaller company should see a benefit from the larger company’s brand, market presence, systems etc and ideally in the same industry the target is in, and the Larger company should see that they can grow the business without destroying any value.
I see this simply as a seed being planted in a green-house. The seed could be a ‘magic bean’ by any means – but in the wrong growing conditions it will never grow and both parties lose.
The only winners would be the targets shareholders, who, if they see any failures in the points regarding culture and operational synergies either wont sell or will take the money and leave.