The end of May means warmer nights and some more consistent temps. However, it is still spring so plant those fragile items with care.
The first thing you might want to think about is your bed. Rake, clear and weed, for sure. Tilling is not necessarily a must but you might consider the state of your soil. Many tout the successes of compost, mushrooms, seaweed or other form of amendment, although Monte Skarsgard breaks with conventional thinking recommending little to no soil amendment (see his latest piece here).
Make sure you have a reliable and consistent water source. Soaker hoses do the job, drip irrigation or simply flooding from a nearby ditch are all good choices. Whatever you do, don’t be like me and think you’ll remember to water—you won’t. If you don’t have access to a ditch, putting a timer on the hose bib assures that your garden gets what it needs, even if you forget.
By now, it’s okay to transplant tomatoes. Even basil is mostly okay to plant now.
If you want to avoid attracting squash bugs, wait until after July 4th to plant watermelon, winter and summer squash and cantaloupe.
A great resource is NMSU. Check out this circular on summer planting: Planting in Summer