If you look at the Starting Hands Chart you will notice that the only time you ever directly call a raise is with a pair. There are, however, a few exceptions: 1) The raise is minimal in size, 2) other players have already called the raise. You can call with suited connectors, as long as both of these criteria are met and you are in position.
http://www.pokerstrategy.com/strategy/bss/1566/1/
Can I call a raise with suited face cards when they connect? E.g. JTs. KQs probably is worse because there is only ace above, so we have less chances to make a straight.
