Although you should keep proof of everything in your back pocket, I dont agree that you should send everything you've ever collected. If the "proof" you are sending in isnt personalized with your name and/or his name, dates etc. it really isnt proof of anything (i've heard of ppl sending business cards, receipts, napkins etc.). I have heard on more than one occasion immigration say to people, for example, that sending in all used calling cards you've ever used (some ppl send 100's) doesnt prove you called that person....they have even said "you could have picked these up on the street".
In my opinion its quality and not quantity:
- send pictures that tell a story, not just of you posing & smiling at the camera. The more candid they are the better. You in a romantic moment, other ppl who dont look like dominicans in the picture, etc. Include a description of that moment/memory on the back of the story. Name the ppl in the picture, etc.
- if you use calling cards to call your partner, dont use a land line but use your cell phone. I know this will kill your minutes, however, you now have that calling card number itemized on your cell phone bill. If you send copies of all your cell phone bills with that number highlighted and you send 1 calling card you are showing how many times you've called with "a card". What i used to do was call my husbands cell directly so that it registered the dominican call and would follow right after with the calling card. send a little note with an explanation of how you use the calling cards etc.
- if you stay at hotels, keep all your receipts of your stay as that will include both your names
- keep copies of your flight receipts, car rental receipts, etc. anything that may have his or your name on it.
- when sending copies of your passport include all the pages not just the ones with stamps on it. This gives them the full picture of your passport & travels. To make it easier, summarize your passport stamps on a cover page giving them the date ranges you travel so they dont have to search for it.
- if you can afford it, go on a real honeymoon outside of the country. There are a few places that accept dominicans without a visa. Ie. Cuba is one of them and its an easy flight from Santo Domingo. This will show that your partner has travelled and has come back, and may give a little more substance to your marriage since they like to know all the details of the wedding (reception, ceremony, guestes, etc.)
Again, its all about organization and quality of the application. My view on this is that if you send too much stuff that has NO significance it makes your application seem messy and overwhelming. As an employee, you can imagine that they would want to look at shorter organized one versus one that looks like it needs a lot of work. Its perception that its less work for them. Ensure you follow the instructions carefully, prepare the package in the order of the checklist and make sure it is all submitted neat and tidy.
I think this has more power than many people think.
I know that I'm contradicting what other ppl are saying, however, my process took all of 8 months with no interview(Sep 2008-Apr 2009) and i think that presentation of facts had alot to do with it.
If by chance you have an interview and they need more proof, you have all that other stuff saved up and could pull it out when you need it. I just dont think its necessary to send "stuff" for the sake of showing volume.
Just my two cents

Good luck to everyone.