HELP with creating a resource pack :S

So I'm making a resource pack for a server I'm on a lot as part of staff and I'm having trouble since this is my first one. When I try to use the texture pack to test textures in-game there are white lines of space between textures that I've edited and I'm not sure what to do Can someone help me? I want to know what to do to fix the pack and make all textures seamless like normal resource packs