Tecky, the best solution is not to start at all, otherwise you'll start telling yourself stuff like, "Oh, the damage is done, so I might as well go all the way..." and it will snowball.
However, you CAN form a new habit - resisting junk food. Experts say that a person needs to do something regularly for three or four weeks for it to become a habit. If you can resist junk food for that time then it will become much easier with time.
You might wish try a few of the mental tricks I developed in oder to break my junk food habit, which included biscuits, hot pies and pastries, cakes and those little mini-pizzas from the bakeries, etc:
What I'd do would be to hold a biscuit or cake in my hand for a few minutes and imagine all the saturated fat from it coursing through my veins. As I did this I looked past my skin into the flesh and organs beneath, trying to visualise the ingested fat as small but thick yellow lumps of lard that would gradually start clotting. Then I'd imagine, just under my chest, lumps of fat sticking to the walls of the arteries around my heart, just inches away from where I held the cake in my hand. I then imagined the pain of a heart attack and, in my final desperate breaths, the regret I would have of leading an unhealthy life and dying needlessly.
There were all sorts of variations of this mental trick I would try:
* Imagining the sugar from cakes coursing through my veins and poisoning my pancreas and liver and then suffering from diabetes and the shortened and lower quality life that illness often brings.
* Visualising the years of future regret that would result from my failure to become healthy now.
If I DID catch myself inadvertently removing a biscuit or cake from one of their numerous breeding colonies in the cupboard or fridge, I would stop it from reaching my gaping maw then calmly, slowly, deliberately drop it into the nearest garbage bin. Junk food IS junk and should be treated as such.
Eventually I formed a habit of refusing junk food as anything except a rare treat on special occasions. This is a huge change from my old self - a guts who would eat anything he saw without hesitation.
I hope the above gives you a few ideas and some inspiration.