Straight hair tips
So your hair is really straight. It could look limp or gorgeously sleek. The difference is in using the right hair products.
What you need is a mousse. Use that for that sleek look. Avoid styling cream as that is too heavy and can make your hair look limp. Try a volumizing mousse instead.

Phyto Phytomousse Volume Shampooing Mousse with Mango Extract ( For Fine & Limp Hair ) 150ml/5.07oz
A natural cleaning agent with innovative foaming mousse formula Enriched with Mango & Shea butter extracts Ensures maximum volume & bounce without weighing down
Sexy Hair Concepts Big Sexy Hair Root Pump Plus Humidity Resistant Volumizing Spray Mousse
Sexy Hair Concepts

Salon Selectives Mousse, Volume Amplifier Va
Salon Selectives

L'Oreal Studio Line Amped Up, Mega Volumizing Mousse, Extreme Hold
L'Oreal Studio Line

Garnier Fructis Style XXL Volume Thickening Mousse, Extreme
Garnier Fructis Style
For more lift, try setting your hair with velcro rollers, then spray on hairspray to hold the curls.

Redken Straight, Hair Straightening Balm
Redken
Philip B. Drop Dead Straight Hair Straightening Baume
Philip B.
Philip B. Drop Dead Straight Hair Straightening Baume
Philip B.

Johnson's Baby No More Tangles Shampoo+Conditioner, Straight Hair
Johnson's Baby
Herbal Essences Dangerously Straight 2 in 1 Pin Straight Shampoo + Conditioner
Herbal Essences
With straight hair, wash your hair frequently especially if it is oily as you want to avoid greasy roots. Also, avoid that razor cut.