Yep, TrekChick has it! Put the downhill ski on first, by standing below it and crossing your downhill leg up to the ski. That will put your leg at the correct angle to just snap right in. Then stand on that ski and put your other ski on; It should go on easily, although the "tip sliding down the hill" thing may still happen. You'll get used to it--jam it a little harder in the snow, or block it with your other ski tip, or use a pole...lots of little tricks.
One thing about that uphill ski (as Schussboelie has also pointed out)--don't try to stand too close to it with your downhill ski when you put it on. If you leave a good amount of space between your skis--that is, step or let the downhill ski slip down a ways, you'll find it easier to keep it on edge to support you while you step into the uphill ski. Ironically, in other words, the way to keep the downhill ski from slipping down the hill while you're trying to put on the uphill ski is to let it slip a ways. The more it slips, the more it tips, until it will hold solidly. Once it holds, leave it there! (I don't know how many times I've seen skiers have this problem--the ski slips, and as soon as it stops, they pick it up and move it back to where it started, only to have it slip downhill again. And again, and again....)
A final trick for putting skis on, especially in soft snow--don't just push down on the heel. Pull up on the toe a little at the same time (making sure the lip of your boot toe is inserted well under the toe piece first, of course).
Lastly--although perhaps this should have gone first--if you've only lost one ski, do not take the other one off. Leave it on, and roll so that it will be the downhill ski when you stand up. Likewise, for anyone who has a hard time getting up without removing skis, take off only one ski--the uphill ski. It is not easier to get up with both skis off, and it is much more of a nuisance to have to put both back on.
You'll get it! But TrekChick's advice is a great trick, and a well-kept secret!
Best regards,
Bob Barnes