Do not play a 30's group. Do not play a 1/4 split.
There is also a tendency for a group that has just had 3 (or more) hit from one group, that in the following game NO numbers from that group will hit, or possibly only one number from that group will hit (40-49 - pick one - maybe).
I don't think a number from 1-9 will come in, but that's not a concrete statement.
I'm still surprised we have not had a 50's grouping hit in forever.