Prominence Poker

You need to accumulate and hold 1 million chips at one time for this achievement. You can do one or more of the following to accomplish that:

Slow and easy method--> Collect daily free chips:
Each day you collect your free chips you get a bonus multiplier. Max multiplier goes up to 5x. If you log in 5 days in a row to collect your free chips, you will be earning around 10k per day (according to your level, you'll get a small difference in the bonus chips. I'm at level 610 (which I think is the maximum current level) and I get around 10.8k per day).
You will mantain the 5x multiplier for each consecutive day you log in. If you miss a day, your bonus multiplier drops back to 1x.

Slow and easy method-->Level up:
Playing head to head tournaments going all in pretty much every hand awards you a quite decent amount of XP which will help you level up.
Leveling up enables you to rank up.
Ranking up awards you big amounts of chips several times as you go up within that same rank and also when you are promoted to the next rank.
As of today there are four ranks within each of the three affiliations. That's many times you can exploit this game feature and receive the rewards for leveling up.

You can combine this strategy with a table item boost. Table items are less expensive on thursdays, when they are 25% off. You can buy as many as you want on thursdays and use them whenever. Also take a look at the hourly events in which smoke and drink items double your bonus XP. Also be sure to check the daily events which award +50% XP. You'll want to focus your effort and time specifically on those days, which are:
-tuesdays --> bonus for tournament play
-wednesdays --> bonus for affiliation outfit
-fridays --> bonus for tourist outfit
-sundays --> bonus for suit/dress outfit
You can find all of this information in http://www.prominencepoker.com --> Events.

Up to now the two tips above work perfectly for everybody with absolutely no knowledge of poker required, involving no amount of skill or luck, so anybody could do it, it will just take its time.

You should get your first million with little to no effort if you don't blow your bankroll in an outfit buying spree or putting it all at risk in those huge pots ring games.

Optional third tip - Playing ranked tournaments
This third tip may be usefull for those who are going also for the "Ranked: Diamond" achievement, and does involve skill and luck.

You could just as easily play tournaments in casual mode, but those tables are always empty and you will need there to be 6 players to maximize your winnings. Also, and most important, you're going to want to hunt those big prizes rewarded for your final standing at the end of the ranked season for up to 1.5 million chips!.
As you rank up and once you make it to the top tiers, large buy-in tournaments award you massive rewards for coming in 1st and winning the tournaments. If you are going for that achievement, you will need to win several of these ranked tournaments, and this is where you can make most of the money in a short time. I managed to make between 100k and 200k daily playing in the gold tier and platinum tier tables.
Also, if you do well and manage to hit (and mantain) Diamond tier which is the highest, at the end of the season you'll get +1.5 millions chips per each Diamond achieved. I made it to diamond this season both in tournament play and head-to-head play, so at the end of this season I will get +3 millions chips in rewards.
For the record, finishing in platinum will give you 500K chips, gold 150k, silver 50k, and bronze 20k.

Hope this detailed explanation helps you. If you are a poker master who could turn 10k chips into 1 million chips at ring games you obviously don't need this at all, but I believe safe and slow is always a nice and comforting alternative for those who aren't as confident in their poker faces, well, avatar faces. Let me know if I can improve this guide in any way before or after you vote.