If your Lookups take a while to open because you have a lot of records, you can limit the number of records that load so they will open quicker. In Controller Module Preferences, you can set the number of records you want to load into your Lookups. The minimum is 10,000 and the maximum is 1,500,000 (if you run Denali in 32bit, Lookups will show a maximum of 100,000 records).

If you’re looking for a specific record that doesn’t appear, you can still use the Contains field at the top of the Lookup to search for it.