THE BASICS

OK, so I'm completely daft and Photoshop seems to be doing everything possible to make my life horrid. How do I make a straight line in Photoshop 6?? I use the "Line Tool" to make a nice design for a template/border, but when I paste it onto my icon, it's not the colour I want, but looks more like I just highlighted the picture (you know, it goes all colourful). Obviously the "paintbrush tool" isn't going to help if one has a shaky hand and the corners go all jagged...

I've been looking around memories for ever and I can't find anything as basic as that... please help! :)