What types of yarn are best for a baby's more sensitive skin?

I think that soft is the most important criteria, whether it's all artificial fiber or a wool blend. I know that for a few decades wool for babies has been out of favor, but remember, babies have been wearing wool successfully for centuries.

With this book, any of the patterns can be made in either of Berroco's fiber blends. Comfort is a wonderfully soft acrylic and nylon blend and Vintage combines those fibers with soft washable wool.

Is sizing ever an issue when making knit or crochet clothes for a baby or toddler?

The great thing about knitting for babies is that they are growing. If your gift is too big at first, they will soon grow into it. So my advice is to be sure it's not going to be too small.

What are your favorite knit or crochet gifts to make for a baby or toddler?

I think that a blanket is the most long-lasting gift. I made the Solaria blanket for our first granddaughter. And a mess of Orangelo Bibs for our first grandson.

For those new to knitting or crochet, what do you recommend they make?

The Citrus Grove Banket is a great first crochet project. It's like a sampler of simple stiches. A new knitter might want to take on the Moderne blanket, or start small with the Orangelo Bib I mentioned above. I find the pattern rather addictive.