I generally give them a meal, not necessarily ones with high energy (small tanks, after all), but things like Tasty Pasta, Tangy Noodles, stuff like that. Things that aren't simple to make and might not be within reach yet.
When I was a newbie, a friend gave me a stack of lemburgers. Best gift ever. Learned how awesome lemburgers could be at early levels, and when I ran out I had the motivation to learn how to find or make them!
A stack of meat, a stack of milk, a stack of low energy food for those itsy bitsy tanks, like lemburgers and grilled cheese, a tool (whatever I have on hand or takes my fancy to make, really, but usually shovel, hoe, or spice mill), a gem to sell for a few quick currants, and a couple of imbued TP scripts, one to Cebarkul to find Glitchen and sell that gem, and one to somewhere random in Roobrik, for quoin jumping. I leave the rest of the slots open so they can put their random stuff in it.
ETA: I forgot, a note with a link to the wiki, and glitch remote, and such useful things.
IMHO to a very large extent give them information and nothing else. Where possible limit the information to slightly vague hints, or links to the encyclopedia or useful utilities such as Glitch Remote.
The two things I remember getting that really helped (without affecting my exploration of the game) were an empty 16-slot bag & a full Random Kindness. I sure needed the extra slots for my new treasures (I had very little money & didn't know where to buy them anyway). And people kept bestowing kindness on me which was great. But I didn't know how they did it. I asked someone who explained what it was. Until a kind stranger gave me one. I was embarassed that I couldn't return the RK. It made a big difference.
I'm one of the recent newcomers and the lucky recipient of several gifts mentioned above. ^_^
Just about everything was immensely useful. The food and items let me achieve more than I could on my own on a single day. But more importantly, they also inspired me to find out more about them and make them on my own, giving a much-needed sense of direction.
Coupled with the kind notes of advice some of you left for me, the experience of starting out was very pleasant and welcoming, like becoming part of a family. So, thank you very much! :-)
(And to the rascals welcoming us with no-no and water: get ready for waves of garlic kiss! Muhawahaha. )
Bags really help newbies, and helps them explore and do stuff on their own. I am a fan of bags and maybe sneaking quion area cards into their pockets. They are just a bit of fun that doesn't take away from their own questing or exploration.
The one thing I do not see in this thread that a few newbies have asked me about is storage furniture. Cabinets and SDBs make good newbie gifts as well. Personally, I'm overflowing with SDBs as I'm still working on that last badge for 251.
@John259: while that's a nice thought, and generally how I answer questions about online games (links to the wiki article with the answer rather than giving the answer, etc.), there's quite a few fish that baby glitchen can't catch with any rod. One player that asked about furniture actually did get a full answer from me (no convenient single wiki article to link to), but she'd still be out of luck while waiting for skills (and I suspect furniture making is not a very useful newbie skill), and completely out of luck coming up with the average 1,500 or so currants for an SDB or cabinet.
Same thing with bags. You can tell them how to get them and where to get them, but that doesn't make them any more within reach than they were before they knew where they were sold. Currants seem easy to vets, but they're a massive struggle to generate until you have many sets of higher skills.