How exactly does one get to the trains from Heathrow?

Maps and links here: http://www.heathrowairport.com/

There is the cheap way and no so cheap. Personaly I take the Heathrow Express that goes directly toPaddington. About $15/head. The walk is a bit long but just follow the signs in the terminal. It is a thirty min run. You could also take the tube around 3/4 dollars ahead but at least two changes and over an hour.

Follow the signs at Heathrow to either the tube or the Heathrow Express. Heathrow Express is ungodly expensive as far as I am concerned, £16.50 (about $26) if purchased in advance online. The price increases to £18 from a ticket machine and £23 onboard. http://www2.heathrowexpress.com/ticket-prices Price on the tube is £5. Travel time is about 35 minutes via the Express, 60 minutes via the tube.

Third option, Heathrow Connect, a 40 minute rail journey with a few intermediate stops for £8.50.

It sounds like this is your first trip, so I'd take the Heathrow Express. On your next trip you can do the tube. You don't mention which airline you're flying, so I don't know your arrival terminal. Generally, you get your luggage and go out of the area. Look for the signs or ask someone. When we flew in on American Air., it was a bit of a winding walk. Sometimes you will have a ticket agent selling round trip Express (HEX) tickets for a few pounds off. We did that the last trip. They have a hand-held credit card machine, but you have to make sure you don't lose the ticket 'cause you need it for your return. The HEX will take you right into Paddington. Others will recommend the Heathrow Connect, which is cheaper, but that gets packed with communters at that time of day. They were not happy with me and my luggage. Ditto the tube for that time of day, which is the cheapest option. Is London your final destination? There is a nice grocery store in the station and some other good food options if you're traveling on.

Once you get out of customs just follow the signs "To Trains" or "Tube" - it absolutely could not be easier. We took the Heathrow Express and loved it. 20 minutes and boom, we're there. Painless and easy as pie.

We took all the advice and Heathrow seems well labeled... We flew in from British Airways... Went Upstairs through customs (one hour due to large crowds and the agents worked quickly and efficiently)... Then downstairs to ground transportation.. we only had carry-on) Then To the right to Heathrow Connect train (free to first stop or to terminals) which is the type of typical airport un-manned train ---it opens its doors when you press the door button to open the sliding doors. We got off at the first stop and got tickets to Paddington (for the the Heathrow Express train) on the ticket machine for 8.50 pounds and waited for train which you reach by walking across to the next set of tracks (no signs, so you may wonder around a bit until you spot an agent who is announcing the trains who will confirm you are on the right track). The train runs ever 30 or so minutes. (don't use the express one as they charge more). This term was confusing to me as they call the train Heathrow Express also. The trip to Paddington was about 30 minutes with about 4-5 stops..At Paddington, it was a bit of nostalgia, chaotic, throw-back-in-time depot but well labeled. (construction, trains, Burger King, more construction tape, a bit dusty, with no clear people paths---like at the airports). We spotted the nationalrail.co.uk area way in the back wall. We bought our train tickets...( cheaper than we could have on-line because of some summer sale and an excellent agent named Chris Mendoza...