For example, you have 2 or 3 tables that have several fields in common. Some might start down the route of generating complex keys (for example, with autonumber or autonumberhash256) and one or more key tables. A second look might reveal that if we simply concatenate all the tables - even though it appears that they are unlikely candidates for concatenation - then we will suddenly be left with a simple key table and some dimension tables.
Another way of simplifying things that I use all the time is ApplyMap. This is a really useful function (not unlike vlookup in excel) that enables us to map small tables into larger tables. Always look to see if you can do a mapping load.
It is often simpler than it looks.