Well, as far as wanting some tips about a visit to a Catholic Church, here goes:
OK, keeping the above suggestions and teaching in mind......WELCOME.
As you enter the Church, you will notice that everyone who comes in dips a finger into a small dish usually attached to the wall containing Holy Water and makes the sign of the Cross (In the name of the Father, Son and Holy Spirit). Try it. Dont worry about doing it wrong. First, touch the finger that touched the water (index, middle, whatever) to your forehead (In the name of the Father) then to the middle of your chest (the Son) and then your left shoulder (and the Holy) then right shoulder(Spirit). The action should be one motion and is one of my favorite things!
Go find a seat. I would go somewhere close (as close as you feel comfortable) so you can see and hear everything the Priest does. For your first time, if you would be more comfortable, sit in the rear of the Church by yourself (if possible). As you approach the entrance to the pews, you will notice that most people will face genuflect, or bow down on one knee and make the sign of the cross. This is done in the direction of the tabernacle, a container usually situated on or near the altar in a place visible to worshipers and festively ornamented (often times in gold). The tabernacle contains the reserved, consecrated hosts..... you bow because you are in the presence of Christ. You can try this too, if you like, but at the very least make the intellectual ascent to try and accept the fact that you are in the room were Jesus Christ is physically, not just spiritually, present.
Next, SMILE.
After you sit down, in front of you, pull down a small padded bench to kneel on later (again, if you feel comfortable). Pull out the book that should be in front of you, take a look at it. This is the Roman Missal (there are many forms of this publication). You will find either in the middle (Sunday) or near the end (non-Sunday) a section marked for the particular day you are attending Mass. The missal contains the text of the daily Scripture reading, so you can at least follow along during the readings.
For the rest of the Mass, I would suggest that you take your cues from the other people attending. Watch them to see when to stand, sit, or kneel....... or just sit there, whatever you want. I would suggest standing when everyone stands. This is generally a sign of great respect in the Mass..... (we stand when a Gospel is read and at other important parts).