Include only the required fields in the page layout. This is especially true for lookup fields and picklist fields, which involve additional processing both while loading and while saving an SFM transaction.

For objects having a large number of fields (> 300), it will be good to define Salesforce Field Sets and associate them with SFM transactions. This limits the number of fields processed to just those relevant to the SFM transaction. This is true even if the default SFM behavior of including all the fields in target object queries does not result in any query failure.

Note that this is applicable only when SFM transactions are launched in the online application.