It really depends on your experience but as a general rule you want to make sure your health values are all good
I always get a complete blood panel done
HORMONES
1. Cortisol, total
2. DHEA Sulfate
13. IGF-1
4: IGFBP-3
5: T3- Free
6. T4, free
7. TSH
8. Testosterone(total, free and weakly bound)
9. hemoglobin A1C
0. Fasting Insulin
Cardiovascular health
1. CBC
2. CMP
3. Lipid Panel
OTHER
14. GGT Important liver value not included in CMP
15. PSA
If any of these values are abnormal take measures to make sure they normalize.
For example if your liver is jacked take Milk thistle, ALA and Primrose oil while training for the next 2-4 weeks. If your test is low get some clomid or HCG and kickstart those bad boys. If your heart is jacked supp with red rice yeast, CoQ-10, Niacin and an omega 3 supplement. If your thyroid is burned out and time isnt doing much to help ive found guggulsterone, tyrosine and phosphates help in this regard. If your prostate is huge then eat ginger by the ton.
all that being equal I ALWAYS overtrain myself in a controlled fashion for about 14 days before I start a cycle. Basically what i mean is I cut carbs and fat by about 50% and rock all kinds of triple drop sets, negatives, 50 rep sets etc to prime my body and clear my receptors for a massive growth surge(think post contest BBer who eats anything that doesnt eat him first after a show, they grow like fuckin weeds for like 2-3 weeks after the show, this is due in massive part to upregulatory effects in the hormonal system)
as a point of fact ive found using DNP for the last 5 days during this phase has enabled me to keep the carbs and fats higher and cut the process down to 11 days with tremendous results.
anyways you decide to do it good luck my friend!