According to decision T 1857/07 (2.4.2) of the EPO boards of appeal, a combination of dependent claims (e.g. 2 and 3) that are both/all dependent on the same independent claim but not each other is not disclosed by the claims (and can therefore not be claimed later rule 123(2) unless disclosed otherwise in the description).
claim 1: xyz
claim 2: xyz as in 1 + a
claim 3: xyz as in 1 + b
Not disclosed: xyz + a + b.
However multiple dependencies cost a lot of money in the US. What's an easy solution to avoid a rule 123(2) when writing a US application so that claiming priority to a the application in Europe doesn't provide grounds for rejection on basis of 123(2) if a combination of the dependent claims needs to be claimed?