As configuring excludefields in that tiny box is painful and incomplete, I use TCEFORM to simplify the TYPO3 backend for editors. I thought in TYPO3 6.x, this would be maybe a bit cleaner, but it's not. Everything's still there, and with FAL, even more potentially user-confusing fields have been introduced.
That's how I do it (in user group TSConfig):
page.TCEFORM.tt_content.longdescURL.disabled = 1
The syntax corresponds to table and column name, AFAIK.
I'll include my current setup (beware, Legacy from 4.5, there are probably black holes in there) in an answer, as it's quite long.
If you disable all fields in a tab, the tab itself will disappear.
The question is:
Is there an easier way? Like, disabling an entire tab at once? Or disabling everything and only including desired fields from the ground up?
Here's my current usergroup TSConfig setup. Attention, this is probably incomplete and may feature outdated items (it's from 4.5).
This could be created automatically from the DB structure, probably. For tx_news, I just got the column titles via
SHOW COLUMNS from tx_news_domain_model_news