Margarine on the bread, cheese, moderately hot pan, but they get weirdly soggy and stick. Too much water in the margarine? Less margarine? This is how I’ve always made them, but suddenly I am a failure. 
I use butter and melt it in the pan first.
Use butter. Most margarines, especially the diet ones, can be over half water.
Sounds like a temperature issue to me. Higher temperature and a preheated pan should resolve it, no?
Too much margarine.
I cook my grilled cheese sandwiches at lower heat, so that the cheese melts before the bread toasts.
Same here. I also cover the pan to help things along, then take it off for the final crisping.
For the OP: if you don’t want to pop for real butter, try using olive oil to toast your sandwiches. Works like a charm.
Olive oil’s good. So’s bacon grease if you’re not too worried about saturated fat. Great with pepper jack or Swiss cheese. If you’re going to use margarine you have to melt it and let some of the water evaporate.
Ewww…margarine? Make sure your pan is evaporating drops of water if you throw it on it. Use butter, cover if you are using cheese thicker than kraft slices (which I never like except for a just-like-my-mom-made-me grilled cheese sandwich).
No problem with butter, but olive oil? Brush it on the bread?
Just always have used marg. for the higher burn point.
The first thing you’re doing wrong is not calling it by it’s proper name…Cheese Toastie. 
Secondly, I have to agree with the butter users. I use butter on the bread with a medium hot pan. I also use Velveeta which has a lower melting point. I cover the pan if I’m using cheddar or other real cheese. You may also want to try a dryer, denser bread. While it’s the staple in our house, white “Wonder Bread” can get soggy pretty quickly.
Heat the pan until you can’t stand to put your hand about two or three inches above for three seconds or so. Butter the bread, not the pan.
Complete the sandwich before you put it in the pan. Lay it carefully down on the hot pan. Leave it. Don’t get curious. I can’t tell you how long because I don’t know your pan, so lift an edge and see if it’s toasty after about three or four minutes. If it is toasty, flip and wait another two minutes. The pan will be getting hotter, so you don’t have to wait as long. Check it to make sure the new side is toasty. That’s how I do it on a non-stick pan.
If you are using stainless or cast iron you have put butter in the pan beforehand to melt and wait for the bread to release after becoming toasty. If you can do this successfully, you are a better cook than me.
Or you can put it on foil or parchment paper under the broiler in your oven. Leave the door slightly open and keep an eye on it. Flip before it burns.
Or, wrap the sandwich in foil and use your iron on the ironing board. Turn, the steam setting off, though. I can’t give you a lot of help on timing this.
Also, after a long commute, wrap it in foil again and put it atop the engine in your car. Close the hood for about four minutes. It may not be toasty but the cheese will be melted.
However, my favorite technique is to wrap the sandwich in foil and take it to the Kīlauea lava flows and bake it until done. Expensive, but well worth the trip.
Hope this helps.
Butter?!? Margarine?!? Quelle horreur! :eek: Mayonnaise, bitches—on both sides of the bread.
MAYO?!! On a grilled cheese?! I think I just threw up in my mouth, eeck
Don’t knock it till you’ve tried it. Perfectly crisped, golden crust every time.
Mayonnaise makes an acceptable substitute if one has no butter.
I had never thought of that but mayonnaise makes perfect sense for frying things. After all it’s only oil, mustard, egg and vinegar or lemon juice, all of which would be fine with many fried things.
My mother always put a slice of tomato in the sandwich. My paternal grandmother made great grilled ham & cheese.
(sigh)
Now I want some Grilled Cheese Sandwiches.
Now what am I going to do?
Do what I did, and make some grilled cheese sandwiches. Then eat them.
Civilised people put dill pickle slices in their grilled cheese sandwiches.
What did you do wrong, you ask?
You used sliced bread instead of flour tortillas, of course.