I] Beginner part:

Try to create a gap between cards of at least one card (or an odd number of cards), that way fewer cards will need to be discarded. If there are at least three spaces, a card can be placed in the middle for free (meaning no discards). At the beginning of the game the stretches of empty spaces are large so try placing a card in the middle. The trick is to place a number that is about half-way between the values of those on either ends of the empty spaces. A larger number can be skewed toward the higher end, with lower numbers toward the lower end.

By placing sequential numbers (i.e. a 4 after a 3, an 11 after 10, etc) you will avoid any gaps in the numbers and need only discard one card. If you can place two (or more) sequential cards in a row where you have several (more than two) empty spaces, place the first card in the middle so you aren’t adjacent another then you won’t need to discard, you can then place the sequential numbered card in an adjacent position and you will only have to discard one card. Taking advantage of this pattern will avoid discarding too many cards unnecessarily.

There are 80 numbers and 36 places, this means the difference between two cards is in average 2,22. Which means the difference between two cards separated by 1 tile is in average 4,5. The difference between lines is 13,33. If you allocate 13 ~ 15 numbers per row, you will be able to distribute the numbers uniformly across the rows and will avoid too many or too few cards on rows. Since there are different symbols on each decade of cards, this allows you to use a ‘rule of thumb’ that you only have two different symbols per row. More, or fewer, than two different symbols per row can point to a problem ahead.

Putting a 2 turn 1 at the second step is fine. It will force the player who will drew the 1 to play it here and to keep it, but you will get a slight advantage on the following steps.

When discarding cards, the worst ones are those which are +2/-2 from another card present on the board, because playing them is never great, and if there is a hole bigger than 2 where you can put that card, there is a good chance another card played two away from it is +4/-4/+5/-5 from the card in question, which still make that card not great.

Pay attention to the number of cards in the deck each player have. If there is too much difference, try to not discard if you have few of them (play not next to others cards), or try to discard if you have lots of them (in end game, sometimes by playing a worst card than the best one).

When playing with Jagged rocks, try to not finish lines too fast. That let you have less chance to have another annoying line locked.

II] Advanced part:

If some cards are missing, when you start, you can expect everyone to play their 1 (or 80) in priority (so at 4 players, turns 1~4). Which means, if you have a 2 (or 79), you should wait until everyone played once before playing that 2 during the second turn (so at 4 players, turns 4~7). And same for the 3 (for 3/78 turns 7~10) even if holding the 3 isn't bad. For those reasons, when playing with manual jagged rocks, try to not lock the top and bottom line in first few turns.

When playing with manual Jagged rocks at 2 players, put it where you wanna play next turn. If you play with more, try to anticipate. Which means, always by default move up or down the ship by 1. If the locked line would be bad (=line empty, while others got lots of cards) or if the lock in your next turn doesn't satisfy you, move it by 2 instead of 1 if possible, or put it in a place where you think your next turn will be fine. It's possible too with more than 2 players to put the ship where you wanna play next turn. In this case, everyone must retain where their next player put their ship to not block that line with it. If a specific player lock the same line twice in a row while still having many choices (imo 5+ lines available), that usually means he can play there twice. There is a possibility it's his only available place to play next turn, but if so, he should usually play this one first then. And it doesn't cost you much to keep that line available for him even after he played there once.