To avoid NaN appearing in calculation results of InfoPath formulas, do the following: Use Now instead of Created.

Try to avoid using the Automatically retrieve data when form is opened option.

If a form is slow and a data connection has the setting Save with form checked, try clearing this option. If data connection still seems to slow down form, delete the data connection and recreate it.

Use a standard prefix on custom data connections—allows you to select them quickly and easily.

Limit of 7 lookup columns per list

Cant filter on lookup column using InfoPath form filters

You cannot create a lookup column on a choice column in another list

Must set filter on both rule for setting value and also on control itself–prevents extra options from appearing based on previous selections

If a form is slow and a data connection has the setting Save with form checked, try clearing this option

If data connection still seems to slow down form, delete the data connection and recreate it

Use a standard prefix on custom data connections—allows you to select them quickly and easily

If you see Only positive integers allowed, this is caused by required multi-item select lookup columns–as designed according to Microsoft

If you use calculated expressions, use filters on them to speed up form

To make calculated expressions display, click Align on Properties tab–if you still do not see text, increase the height of the calculated expressions

Can’t use Contact columns as reference in calculated columns on InfoPath form

?If you change a choice field in list settings, you might need to refresh the INfoPath form fields. I’ve seen persistent choices that were removed from the column settings in the list settings.

You cannot reference ID column in a conditional rule on an InfoPath form.

You can have up to 8 levels of nesting in INfoPath formulas or calculated expressions.