Finding list of points near current long/lat using PostGIS?

Question

[UPDATE]

What I have now is light years better than I did before. With the suggestion to look at ST_POINT, I restarted my googling and the query looks now like so:

SELECT "ID" from "CityBottle".message_locations where location= "CityBottle"."fnMakePoint"( :Longitude,:Latitude)

MakePoint is a function defined like so:

BEGIN
 RETURN CAST(ST_SetSRID(ST_Point(Longitude, Latitude),4326) As geography);
END;

It is worth noting that I did notice the function ST_MAKEPOINT, but I am at the prototype stage right now and the above was good enough (plus, I would probably still wrap that into a custom function to protect the queries...).

Now, the main contention I have is "how do I define a reasonable index"? I mean, the points are in their own table and I am accessing the whole thing via a view to list the messages (the table has a query only to make sure that the point isn't already in the table...).

Thus, I'll need some kind of index that will work properly so that I can use ST_DWithin.

Can I just create an index on the field? Is there anything specific I need to do for better performance?

[ORIGINAL]

What I need is a "where am I?" kind of thing listing points within a certain radius from the current POINT(long,lat) .

My understanding is that you do this with ST_DISTANCE and saying that it has to be, for example, less than a certain amount.

My first attempt has been this:

select* from "CityBottle".message_locations ml where ST_DISTANCE(ml.location,POINT(12.0,13,0)) < 100

which has yielded this error message:

ERROR:  function point(numeric, integer, integer) does not exist
LINE 1: ...essage_locations ml where ST_DISTANCE(ml.location,POINT(12.0...
                                                             ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.

Suggestions?