When you cannot physically aid anyone, when you cannot be of service in any other way, pray and meditate. Always for God's will for you and the power to carry it out, and for the benefit of others. Spend twenty minutes as you lay in bed prior to sleep and send out as much love as you can.
Repeating earlier suggestions, as you cannot get enough:
-"I am praying for the greatest possible good for Mankind and all involved". (ASAH forum)
-"I am praying for the enlightenment of all sentient beings." (Tibetan)
-"I am love, I am giving love." (Young-Sowers Divination Deck)
-"I am praying that all of the lost, hear God's call home." (Angels)
And always, if you are suffering from some particular fear or difficulty, pray that all others who share in it, are healed/delivered from it with grace and ease.
-"We are praying that all of the falsely imprisoned are freed."
-"We are praying for positive abundance for all in need."
-"We are praying that all of the hungry are fed."
-"We are praying God's will for all of Creation."
-"White Light throughout Earth and The Universe."
-"We are praying the cures for cancer are given to Mankind."
-"God bless Creation."
What works for me is a slight derivation on Buddhist techniques on Mindful Breathing, which are based upon the Anapanasati Sutra's 16 stage course. The breath is a tool of transmutation. Let the body "waterbed" and mentally state the prayer on each in breath and on each out breath (or split it between in and out if it is too long). Keep light attention upon the breath as it moves through the nasal passage, and if possible, also be aware of its movement into and out of the lungs within the body, and of the volume of air just outside of the body. It takes practice, like anything, and it is a technique some two-and-a-half millennia old. It has lasted because it works. It adds power to prayer!
The passion of the Baptists is another way to charge up your prayers. If you really mean it, if your heart is involved, your prayers carry that energy and are thus far more than repeated words.
Prayer during meditation is also powerful. The body is stilled, the mind separate; with attention on the spine and its base, prayer centered there can have even more depth. Centering the energy just behind the base of the spine, behind the body, is also good (anyone who meditates knows).