reselecting previously selected text (i use this to fix botched selections):

gv  " :h gv for more
    " you can use `o` in visual mode to go to the `Other` end of the selection
    " use a motion to fix the selection

reselecting previously yanked text:

`[v`]
`[         " marks the beginning of the previously yanked text   :h `[
`]         " marks the end                                       :h `]
 v         " visual select everything in between

nnoremap gb `[v`]    " "a quick map to perform the above

pasting and indenting text (in one go):

]p   " put (p) and adjust indent to current line
]P   " put the text before the cursor (P) and adjust indent to current line