I am assuming you have a manual (try to include year, make, model, mileage and anything relevant to your troubles in your posts)
The linkages come in on the driver's side of the engine, closer to the firewall. If you know where the starter is, then you can find the linkages (they are slightly further towards the firewall than the starter) One should have an orange cap, and the other black(??). They go right in to the top of the bellhousing.
Have someone row through the gears for you, and make sure that both linkages both freely throughout their range.
Also, check underneath your shifter boot (on the interior of the car).. the links that connect your shifter rod to the rods that lead to the tranny can come undone..) boot pops off, after you remove the shifter knob.
There is a recent thread (2 weeks) in troubleshooting, including pictures of the interior shifter area....
Ray