Syntax quick reference: *bold* _italic_ [spoiler]hide text[/spoiler] @code@ +underline+ -strike- ^sup^ ~sub~ [==stuff you don't want textile to parse==]
Links: "On-site link":/some-link, "External link":http://some-link
Images: >>1 — link to image, >>1t — embed image thumbnail (>>1p — large preview, >>1s — small thumbnail)
External images: !http://some-image!, !http://some-clickable-image!:http://some-link
Remember to use embeds (>>) for booru images as these let users filter content they don't want to see
(I'd use it)