How to not tie with Marines?

So, im finally getting some games o' 40k after a couple month painting hiatus and I must ask the 40k community, how do I win with space marines? I dont always seem to be making the strongest tactical decisions, however even when I do I cant seem to pull out that strong victory yet with this army. Ive been playing in smaller point games (about 1000 to 1250 point games) with the core of my army:

HQ - Captain
- Command Squad in Razorback, Melta Gun, Company Champion
Troops - 2x Tactical Squad (Melta Gun, Rocket Launcher) I typically combat squad
Elite - 5x TH/SS Termies
- Dreadnought (H. Flamer, M.Melta)
Fast Attack - 5x Assault Marines (Power Fist)
Heavy - Predator

and I keep drawing with the last squad I have on the table to hold that last objective. Typically, I seem to have 8 marines left on the table while im still facing a formidable army from my opponent. I just cant kill as much as I die with the vanilla marines codex.

So, I think you all may have seen my army list from previous post (here), so now its time to begin working with my core list and expanding outward to bigger and better things. More to come with what I dream up, and ill take any suggestions.

I know suggestion #1 to myself is to just keep at it, keep on playing away and tactics will come with experience.