android - Changing layout on multiple devices? -

i'm sure there's basic answer i'm still learning , i'm not quite sure. have app few button on start screen. works on nexus 1 (emulator) , samsung s2 (device); because screen size same. however, when preview screens on tablets example button spread out , small. on other devices they're halfway each other , doesn't good. i've tried match_parent , wrap_content doesn't help, how use .xml code or layout properties make sure button's don't budge each other yet fill screen (i'm using relative layout)?! thank's can answer.

is there in layout_height/width/align change?

<button     android:id="@+id/button10"     android:layout_width="match_parent"     android:layout_height="wrap_content"     android:layout_alignbaseline="@+id/button9"     android:layout_alignbottom="@+id/button9"     android:layout_alignright="@+id/button8"     android:text="info" /> 

you need make seperate layouts different screen sizes , densities

http://developer.android.com/training/basics/supporting-devices/screens.html