Ouchy, scorchy tongue sucks! Some tips to reduce the evil tongue bite:
1 - Use a 'filtered' pipe (9mm filter / Savinelli with Balsa Filter / Brigham with Maple Rock filter) as it takes out much of the moisture and chemicals from the air stream.
2 - Use a cool-burning natural tobacco blend. I'd suggest Dunhill Nightcap if you like campfires, MacBarren Golden Extra if you like Burley, or MacBarren Navy Flake if you like sweet Virginia with a little honey flavoring.
3 - Smoke sloooooooooooowly. Take a tiny sip and count to 15 in your head, then take another. If that's not enough to keep the tobacco lit, either sip harder or smoke faster (count to 10)...
4 - Dry out your tobacco for half an hour before filling the bowl. Greatly helps some of those nasty humectants to evaporate, instead of getting fired up and putting a chemical burn to your mouth.
5 - Pair your smoke with Green Tea, or coffee.
6 - Refrain from smoking a pipe too much until your mouth heals. Like you wont go scratch a wound every hour you shouldn't keep on burning your tongue. Give it a day or two rest and then start again. Keep it to two bowls a day to give your pipe and your mouth adequate recovery time.
7 - Gotta get through the tongue burn. Every new pipe smoker experiences it. You'll build up a resistance pretty fast. Takes about two weeks I'd say. After that it's smooth sailing ;-)