I use this:
HTML:
User-agent: *
Disallow: /ajax.php
Disallow: /asset.php
Disallow: /assetmanage.php
Disallow: /attachment_inlinemod.php
Disallow: /attachment.php
Disallow: /attachments/
Disallow: /blog_ajax.php
Disallow: /blog_external.php
Disallow: /blog_inlinemod.php
Disallow: /blog_report.php
Disallow: /blog_search.php
Disallow: /blog_subscription.php
Disallow: /blog_usercp.php
Disallow: /calendar.php
Disallow: /clientscript/
Disallow: /converse.php
Disallow: /cpstyles/
Disallow: /cron.php
Disallow: /customavatars/
Disallow: /customgroupicons/
Disallow: /customprofilepics/
Disallow: /editor.php
Disallow: /editpost.php
Disallow: /external.php
Disallow: /forumrunner/
Disallow: /global.php
Disallow: /group_inlinemod.php
Disallow: /groupsubscription.php
Disallow: /images/
Disallow: /img/
Disallow: /includes/
Disallow: /infraction.php
Disallow: /inlinemod.php
Disallow: /install/
Disallow: /joinrequests.php
Disallow: /list.php
Disallow: /login.php
Disallow: /member.php
Disallow: /memberlist.php
Disallow: /members/
Disallow: /misc.php
Disallow: /mobiquo/
Disallow: /moderator.php
Disallow: /newattachment.php
Disallow: /newreply.php
Disallow: /newthread.php
Disallow: /online.php
Disallow: /packages/
Disallow: /payment_gateway.php
Disallow: /payments.php
Disallow: /picture_inlinemod.php
Disallow: /picture.php
Disallow: /picturecomment.php
Disallow: /poll.php
Disallow: /posthistory.php
Disallow: /postings.php
Disallow: /printthread.php
Disallow: /private.php
Disallow: /profile.php
Disallow: /register.php
Disallow: /report.php
Disallow: /reputation.php
Disallow: /search.php
Disallow: /sendmessage.php
Disallow: /showgroups.php
Disallow: /showpost.php
Disallow: /signaturepics/
Disallow: /store_sitemap/
Disallow: /subscription.php
Disallow: /tags.php
Disallow: /threadrate.php
Disallow: /threadtag.php
Disallow: /usercp.php
Disallow: /usernote.php
Disallow: /vb/
Disallow: /visitormessage.php
Disallow: /widget.php
Interestingly, this also makes the google mobile friendly test pass, even if you're not really mobile friendly at all.
Keep in mind this is a publicly viewable document, as it has to be in order for it to work at all - and so therefore keep your admincp and modcp and any other area you don't want to announce publicly, OFF this list. The bad bots are gonna index those anyway.