If you just run Autokern from the Tools menu FontCreator will do a lot of the donkey work for you. I prefer to do it manually to have more control over how the kerning classes are named and which glyphs they contain. Try it both ways and see which you prefer.
It’s definitely worth the extra effort to use Class-based kerning even if your font only includes the ANSI character set. If it only uses Latin Basic, then there is no need, but even an ANSI font contains several versions of A i.e. Á,À,Ä,Ã, and Å that will use the same kerning pair adjustments a AT and TA, AO and OA, AV and VA, AW and WA, AY and YA, and AC, AG, DA etc.
See, even without mentioning lowercase pairing (Ay) or pairs with figures (A0), we have quite a lot of kerning pairs already. With @A_Caps class, and @VW_Caps class we need to manually adjust far fewer pairs.
Watch the Using Kerning Classes video for FC 9.0 on my FontCreator Review page to get to grips with the process of creating a comprehensive kerning pairs lookup.
What I did, was create an OpenType Feature script for Garava Regular, then I imported that into Garava Italic, Bold, and Bold Italic¹. After importing the script, I ran the Autokern feature to let FontCreator adjust the pair values, and manually checked the 500 or more pairs for anomalies. My fonts are large and some like Garava include both Small Capitals and Petite Capitals, which are all kerned: Garava has 33K kerning pairs. Checking 1,000 pairs is a lot faster than checking 33,000.
A normal ANSI font won’t need nearly that many kerning pairs.
¹ The entire OpenType script can be imported to save reproducing ligatures, etc., for each type style. OpenType Layout Definition Scripts can be imported into other fonts too. If they have the exact same glyph coverage, there won’t be any errors to fix.