To interactively test things use:

~%> bitbake -i

this will open the bitbake shell. From here there are a lot of commands available (try help).

First thing you will want to do is parse all of the recipes (recent bitbake version do this automatically when needed, so you don't need to manually do this anymore):

BB>> parse

You can now build a specific recipe:

BB>> build net-snmp

If it fails you may want to clean the build before trying again:

BB>> clean net-snmp

If you update the recipe by editing the .bb file (to fix some issues) then you will want to clean the package, reparse the modified recipe, and the build again:

BB>> clean net-snmp
BB>> reparse net-snmp
BB>> build net-snmp

Note that you can use wildcards in the bitbake shell as well:

BB>> build t*