I assume you're currently looking at the MileagePlus Explorer Card?
The best non-targeted offer for the MPE is a 50K sign-up bonus, plus 5K for adding another user within two months, plus 10K for spending 25K within a calendar year, plus free first bag check for two ($100/flt), plus two United Club passes per year ($100/yr), plus first year fee waiver ($95). To find this offer be sure you already have a UA/MP account with a balance of at least one mile. If you need help with that just let me know. Once you have at least one mile you should clear your cache and sign in to MP again. Look for this advertisement...

That's the easy way. However, if you're willing to put a little more effort into it then I'd probably try for a three-way chain.
Start with the Chase Sapphire Preferred card (40K). Thanks to some recent changes you'll receive a lower initial sign-up bonus versus the MileagePlus Explorer card. However, you'll also gain more flexibility than straight UA/MP points and have a better overall earn ratio. Since you're not exactly married to United these points can be transferred to whichever carrier has availability on dates you can work with. And that's what's most important really. There's no guarantee you'd ever be able to book the direct flight on a saver award anyway, which is what I'm guessing you're going for.
Here's where things start to get interesting. You can combine a Sapphire Preferred with an Ink Bold small business card (50K) on the same UR account. You can also apply for both at the same time without running afoul of Chase's automated credit risk assessment algorithms. There is a lot you can do with the Ink Bold card, but the primary benefit is that it earns 5x points on office supplies, including some prepaid debit cards.
After you've met the minimum spend on both of those cards you can chain a third card in the form of a Chase Freedom (30K IIRC), which earns UR points that are not normally transferable but become "unlocked" with an active Sapphire Preferred account mentioned in the first step. The main benefit for Freedom is that it has a rotating 5x bonus. Carefully planning your spending to match up with the bonus rotation can result in a substantial improvement in your point accrual over the CSP and leagues better than the United MileagePlus Explorer card.
Counting the minimum spend points, you should be approaching something like 130,000 UR points that can be transferred to anyone's UA/MP account. If you never carry a balance, move all your points before closing the first card, and cancel all cards by the 11-month mark you shouldn't be owing anybody any additional fees. As always YMMV, but that's what I would probably do.
The next big/flexible program for domestic use would be AA's AAdvantage/One World. I'd say they're pretty much on par after the not-so-beneficial UA/CO merger. If you use the dual sign-up trick you can secure 100k AA points for $6k worth of spending in three months and then add a business card for another 50k after you've cleared the first two hurtles.
All of these suggestions are per person, so if everyone can meet all of the minimum spend requirements with conventional spending you could have several hundred thousand points in no time at all.
In exchange for this (and any future) advice I only ask one thing. Please think twice about using points for travel and then criticizing others for saying today's revenue fares are too expensive. Everyone is entitled to their own opinion, including those who'd rather not spend $1,000 or more for a 1970's fiberglass bedroom that makes solitary confinement look spacious.
Edited by Texas Sunset, 19 June 2012 - 07:59 AM.
Any views expressed are my own and do not represent the views of my employer, parent companies, partners, or subsidiaries.
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