At Yeti we build both Android and iOS applications for our clients. In order to get a pre-release app onto a client's device for testing and approval there are a couple hoops to jump through.
Android makes the process easy. We generally put the application, which is saved as a .apk file, onto a web server and then send the link over (ex: yetihq.com/your_app.apk). If this linked is visited on an android phone it will simply pop open a dialog that asks you to install. Press "Yes" and presto, the app is on your Android device.
Apple on the other hand, even though we love them, makes the process a little difficult and confusing. This is due to how protective the business is and how locked down they try and keep the devices.
1.) We need to get the UDID (Unique Device Identifier) number of any device that will be testing the app. This can be done by downloading this app http://itunes.apple.com/us/app/udid/id385936840?mt=8, hitting "Send UDID" and putting in the email address of your developer.
2.) The developer will then "provision" the devices and create a build. They will then send a provisioning file and the app itself over attached in an email.
3.) Open iTunes with your iPhone/iPad/iPod plugged in. Take the .mobileprovision file and drag it onto "Applications" in the left sidebar of iTunes.
4.) The application will most likely be in a .zip file, quickly unzip the file to get the .app thats inside. Drag this file to the same place you dragged the .mobileprovision
5.) Sync your device with iTunes and you should be all set. If it is not working, try restarting the device and doing it again or contact your friendly developer! This process isn't the most ideal but sadly the reality we are stuck in, if you are getting errors be sure to write them down and let your developer know so he can get it fixed up right away.