This is a horrible grind, but luckily the game is quite enjoyable and it's getting very addicting when you try to beat the scores of your friend. For this achievement however, you shouldn't focus on getting big scores as the game gives you close to nothing when it comes to in-game coins. I will share you the strategy I'm currently using, and in my case it's really paying off. I could see why people wouldn't use this if they found something better, but feel free to share it with me as I'm currently going for this. The described method can also be used to unlock:
1. LEARN THE GAME
This is obvious, so I'll keep it at this. Remember to go for lines directly when your game starts and go in Frenzy-mode as fast as possible as that will be a big help to clear more lines at once. There are also Pro-video's available in the game since the last update, which should help you clear more lines once you've figured out the methods the devs are using.
2. DON'T USE FINISHERS
Finishers are quite expensive and don't pay off when it comes to clearing lines but it does when it comes to big scores. Personally I didn't spend coins on them and mostly got them by the gambling wheel which brings me to my next point.
3. BOOT YOUR GAME EVERY 4 HOURS
Every 4 hours you will receive a free spin and the ones you already received will be marked out. That being said, it should be impossible to land on the same tile twice in a row. You could be the lucky guy getting 100,000 in-game coins or you could get unlucky and only receive 1,000. Either way, be happy with what you get, as every little bit helps.
4. LEARN THE PURPOSE OF THE POWER UPS
As a guys who spent real money to buy the Pro Pack, I can say that not every power up is really good when it comes to clearing lines. Personally I'm currently using the Power Up of The Week along with Lasers. The Lasers can clear your board which could cause a huge cascade when you enter Frenzy, which again, is good to get done with this grind as soon as possible. Other good power ups in my eyes would be Avalanche, Quake and Lucky Seven. All the others can be used to increase your timer or getting more points, which doesn't really help you getting 100,000 lines. Be wise and find the power up that suits you best. I'm currently getting 100+ lines for every game I finish, so maybe you could try my tactic and see how far you get.
5. AIM FOR A HIGH IN-GAME LEVEL
As said in the solution from https://www.trueachievements.com/DOA+hed.htm
, you will need to aim for level 35 of higher; depending on how many power ups you use. The grind is ridiculously long in hours (I'm 25 hours busy at the time of writing), so prepare to invest a lot of time.
I hope I helped some of you with these hints. As written before, every one has his own play styles so don't downvote this solution because it doesn't suit you. Let me know what you guys are currently using so I can perhaps change my own tactics and improve this solution.
Good luck guys!