Sooner or later, you will run out of chips, which means that you will have to take a card. Therefore, especially at the beginning of the game, don't be too hesitant about taking a card that doesn't have that many chips next to it. A 15, for example, with three or four chips next to it, may well be worth considering.
A good way to grab as many chips as possible is to decline a card which you yourself could easily take (because it would complete or add to one of your sequences), but which your fellow players won't want (because it would get them too many points).
Just send it around for another turn or two; it will come back to you with a lot more chips.
Example: Sabrina already has the 34 in front of her. The next card to be turned over is the 35. Sabrina could take it at once, as it would allow her to form a sequence with the 34 she already has.
Her fellow players, however, do not want to take the 35 at all, because to them it's worth 35 points. Thus, Sabrina doesn't accept the 35 on her turn, but declines it, waiting until it comes back her way with a decent number of chips.
Note: Of course, you can try to send a very high card around several times, but you shouldn't get too greedy! When some other player runs out of chips, he will have to take it - and you can never know when that moment will come.
Since nine cards are put aside at the beginning of the game, there will necessarily be a few gaps between the cards. Of course, you'll have to speculate upon being able to close gaps between some of your cards at a later point (for example, between the 22 and the 24) - a little luck is part of the game - but you can never rely on that happening.
The bigger the gap (say, between the 30 and the 35), the smaller the chance that all necessary cards to close it are in the deck - and that you will get them all.
If you want to put a little more emphasis on tactics, you can try the following variant rule: At the beginning of the game, each player only gets 10 chips. The cards with the numbers 10, 20 and 30 are taken out and put into the box, before the 24 cards for the deck are counted off (face-down).
The six cards which then remain are also put into the box. The rest of the game is unchanged, but knowing three of the nine gaps in advance increases the tactical element of the game.