1.I add my nutrients? 2.then check ph? 3.then ph up/down ?

Yes, however it might be beneficial to test and adjust pH (if necessary) before you add the nutrients as well. I did at first, but just don't anymore. Though if the pH is above 7 it can cause the mineral elements to bind up (precipitate), thus not be available to the plants even after you adjust the pH afterword.

P.S. My personal opinion is you will be much better off using the inexpensive pH drops, instead of a pH meter. The drops will never give you false readings, the drops don't need to be calibrated and cared for, and one bottle lasts me well over 6 months. The directions call for filling the vial half way, and using 3-5 drops. I fill the vial 1/6 (that's 1/3 of half the vial) and use 1 drop. One drop one test. The bottle lasts a long time. Calibration fluid for a meter alone will cost you more, and the meters can give false readings.

And what should the ph be? 5.5?

pH for hydroponic plants is can be a little different for different plants, as well as under different growing conditions (temp, humidity, phase of growth etc.), but generally ranges from about 5.5 to 6.5, in some cases can be as high as 7.0. But most all plants will do well at about 6.0. Don't worry about how exact it is, plants actually do better with a range like 5.5-6.5 rather than an exact pH like 5.8 or 6.3. so don't spend time and effort trying to keep it perfect, just keep it in range. Here is a link to a list of plants and pH ranges Vegetables (links to pH ranges for fruit, herbs, and flowers at the top left of the page).

And if I use declorinated tap should I get a ppm meter do they make a 2 in one ph/ppm meter? Because I see there is a "hard water micro" in the gh line.

A PPM/TDS or EC meter wont be able to tell you what's in the water, that's just a fundamental flaw in their capabilities. It's also the reason I don't even have any of them, they just cant do the only thing I want them to be able to do. Use the hard water micro nutrients as a last resort. Their not intended to be an answer to bad water quality, but just an option when using good quality water just isn't possible. What's in your tap water will vary from one area to another, even from one house to another in the same city, and can even change from day to day in the same house. You can have the water tested, but for what you would pay for that (or a PPM/TDS or EC meter for that matter), you could have invested in a water filter, and had a reliable water quality source to begin with. Where a PPM/TDS or EC meter will only tell you what quantity of "unknown" elements are in the water.

And should I go half strength?

My rule of thumb generally goes something like this:

1. For seeds, plain water.
2. For seedlings (with the first set of true leaves), 1/4 strength.
3. Once they get a few inches tall, 1/2 strength.
4. Then in a week or two after that when they have at least doubled in size, go full strength.

If it's hot weather, no more than 3/4 strength. And sometimes I'll mix it somewhere between 75% and 90% (about 60% to 75% in hot weather) just because it's generally better to mix on the weak side anyway. But I really just go by the way they look to let me know when to change the nutrient solution, as well as when to increase or decrease the strength of the nutrient solution. I look for things like yellowing/discoloration of the leaves, as well as slowing growth, and/or quick pH swings.

Thanks alot for sharing. I will make sure to stay 1/2 strenth. I cant wait to try DWC. I am also looking into the aeroponic tub sysem or diy i believe it is called. I may just go aero. The reason I have been soiless/soil is because of its forgiving ways but now I am ready to see real results so I will try either DWC or DIY. I am choosing these because they are esay to construct but one day I want to try those aeroponic "tubes" with one res it seams like less work but a little hard to work.
Thanks.