Use the command line tool mdutil.

For example, say you connect an HFS+ journaled volume named "LEAVE_ME_BE"

Use the following command to disable indexing of the volume. If ownership is enabled, running as sudo may be necessary:

sudo mdutil -i off /Volumes/LEAVE_ME_BE

Check indexing status of all connected volumes:

mdutil -s /Volumes/*

Read the man page linked above for further options (disabling spotlight for the volume all together, etc.)

Use the command line tool mdutil.

For example, say you connect an HFS+ journaled volume named "LEAVE_ME_BE"

Use the following command to disable indexing of the volume. If ownership is enabled, running as sudo may be necessary:

sudo mdutil -i off /Volumes/LEAVE_ME_BE

Check indexing status of all connected volumes:

mdutil -s /Volumes/*

Read the man page linked above for further options.